feed.xml

<?xml version="1.0" encoding="utf-8"?><?xml-stylesheet type="text/xml" href="/feed.xslt.xml"?><feed xmlns="http://www.w3.org/2005/Atom"><generator uri="http://jekyllrb.com" version="3.2.1">Jekyll</generator><link href="https://ckape.github.io/workhard/feed.xml" rel="self" type="application/atom+xml" /><link href="https://ckape.github.io/workhard/" rel="alternate" type="text/html" /><updated>2016-09-22T22:57:56+08:00</updated><id>https://ckape.github.io/workhard/</id><title type="html">WorkHard-Website</title><subtitle>This is my own site.</subtitle><entry><title type="html">Java源码分析——TreeMap</title><link href="https://ckape.github.io/workhard/TreeMap/" rel="alternate" type="text/html" title="Java源码分析——TreeMap" /><published>2016-09-22T00:00:00+08:00</published><updated>2016-09-22T00:00:00+08:00</updated><id>https://ckape.github.io/workhard/TreeMap</id><content type="html" xml:base="https://ckape.github.io/workhard/TreeMap/">&lt;h2 id=&quot;treemap&quot;&gt;TreeMap&lt;/h2&gt;
&lt;blockquote&gt;
  &lt;p&gt;参考学习资料：
&lt;a href=&quot;http://blog.csdn.net/eson_15/article/details/51217741&quot;&gt;java集合框架10——TreeMap和源码分析（一）&lt;/a&gt;&lt;/p&gt;
&lt;/blockquote&gt;

&lt;ol&gt;
  &lt;li&gt;
    &lt;p&gt;简介
跟HashMap一样，TreeMap也是一个 &lt;strong&gt;非线程安全&lt;/strong&gt; 的集合，不同的是，TreeMap是有序集合，内部是通过 &lt;strong&gt;红黑树&lt;/strong&gt; 实现的。【可爱的传送门：&lt;a href=&quot;http://blog.csdn.net/eson_15/article/details/51144079&quot;&gt;红黑树介绍&lt;/a&gt;】该映射根据其key的自然顺序进行排序，或者根据用户自定义的Comarotor进行排序。&lt;/p&gt;
  &lt;/li&gt;
  &lt;li&gt;
    &lt;p&gt;源码分析（jdk1.7）&lt;/p&gt;
  &lt;/li&gt;
&lt;/ol&gt;</content><category term="JavaBasic" /><summary type="html">TreeMap源码分析.</summary></entry><entry><title type="html">Project Test</title><link href="https://ckape.github.io/workhard/Project/" rel="alternate" type="text/html" title="Project Test" /><published>2016-09-21T00:00:00+08:00</published><updated>2016-09-21T00:00:00+08:00</updated><id>https://ckape.github.io/workhard/Project</id><content type="html" xml:base="https://ckape.github.io/workhard/Project/">&lt;h1 id=&quot;project&quot;&gt;Project&lt;/h1&gt;</content><category term="Project" /><summary type="html">Project Test.</summary></entry><entry><title type="html">Java源码分析——HashSet</title><link href="https://ckape.github.io/workhard/HashSet/" rel="alternate" type="text/html" title="Java源码分析——HashSet" /><published>2016-09-21T00:00:00+08:00</published><updated>2016-09-21T00:00:00+08:00</updated><id>https://ckape.github.io/workhard/HashSet</id><content type="html" xml:base="https://ckape.github.io/workhard/HashSet/">&lt;h1 id=&quot;set&quot;&gt;Set&lt;/h1&gt;
&lt;ol&gt;
  &lt;li&gt;&lt;strong&gt;HashSet&lt;/strong&gt;
    &lt;ul&gt;
      &lt;li&gt;Serializable&lt;/li&gt;
      &lt;li&gt;Cloneable&lt;/li&gt;
      &lt;li&gt;Iterable&lt;E&gt;&lt;/E&gt;&lt;/li&gt;
      &lt;li&gt;Collection&lt;E&gt;&lt;/E&gt;&lt;/li&gt;
      &lt;li&gt;Set&lt;E&gt;&lt;/E&gt;&lt;/li&gt;
    &lt;/ul&gt;
  &lt;/li&gt;
  &lt;li&gt;&lt;strong&gt;TreeSet&lt;/strong&gt;
    &lt;ul&gt;
      &lt;li&gt;Serializable&lt;/li&gt;
      &lt;li&gt;Cloneable&lt;/li&gt;
      &lt;li&gt;Iterable&lt;E&gt;&lt;/E&gt;&lt;/li&gt;
      &lt;li&gt;Collection&lt;E&gt;&lt;/E&gt;&lt;/li&gt;
      &lt;li&gt;NavigableSet&lt;E&gt;&lt;/E&gt;&lt;/li&gt;
      &lt;li&gt;Set&lt;E&gt;&lt;/E&gt;&lt;/li&gt;
      &lt;li&gt;SortedSet&lt;E&gt;&lt;/E&gt;&lt;/li&gt;
    &lt;/ul&gt;
  &lt;/li&gt;
  &lt;li&gt;&lt;strong&gt;LinkedHashSet&lt;/strong&gt;&lt;/li&gt;
  &lt;li&gt;&lt;strong&gt;CopyOnWriteArraySet&lt;/strong&gt;&lt;/li&gt;
  &lt;li&gt;&lt;strong&gt;AbstractSet&lt;/strong&gt;&lt;/li&gt;
  &lt;li&gt;&lt;strong&gt;ConcurrentSkipListSet&lt;/strong&gt;&lt;/li&gt;
  &lt;li&gt;&lt;strong&gt;EnumSet&lt;/strong&gt;&lt;/li&gt;
  &lt;li&gt;&lt;strong&gt;JobStateReasons&lt;/strong&gt;&lt;/li&gt;
&lt;/ol&gt;

&lt;h2 id=&quot;hashsethashmap&quot;&gt;HashSet（本质上是HashMap）&lt;/h2&gt;
&lt;p&gt;所以先看HashMap的源码&lt;/p&gt;

&lt;p&gt;&lt;strong&gt;其实就是基于HashMap实现的，用key放置值，value则存放一个final，static的对象PRESENT&lt;/strong&gt;&lt;/p&gt;</content><category term="JavaBasic" /><summary type="html">HashSet源码分析.</summary></entry><entry><title type="html">Java源码分析——HashMap</title><link href="https://ckape.github.io/workhard/HashMap/" rel="alternate" type="text/html" title="Java源码分析——HashMap" /><published>2016-09-21T00:00:00+08:00</published><updated>2016-09-21T00:00:00+08:00</updated><id>https://ckape.github.io/workhard/HashMap</id><content type="html" xml:base="https://ckape.github.io/workhard/HashMap/">&lt;h1 id=&quot;map&quot;&gt;Map&lt;/h1&gt;
&lt;ol&gt;
  &lt;li&gt;HashMap（常用）&lt;/li&gt;
  &lt;li&gt;TreeMap（常用）&lt;/li&gt;
  &lt;li&gt;ConcurrentHashMap（并发）&lt;/li&gt;
  &lt;li&gt;EnumMap（枚举map）&lt;/li&gt;
  &lt;li&gt;Hashtable&lt;/li&gt;
  &lt;li&gt;LinkedHashMap&lt;/li&gt;
&lt;/ol&gt;

&lt;h2 id=&quot;hashmap&quot;&gt;HashMap&lt;/h2&gt;
&lt;ol&gt;
  &lt;li&gt;map
    &lt;ul&gt;
      &lt;li&gt;定义
        &lt;blockquote&gt;
          &lt;p&gt;一个把键映射到值的对象被称作一个映射表对象。映射表不能包含重复的键，每个键至多可以与一个值关联。Map接口提供了三个集合视图：键的集合视图、值的集合视图以及键值对的集合视图。一个映射表的顺序取决于它的集合视图的迭代器返回元素的顺序。一些Map接口的具体实现（比如TreeMap）保证元素有一定的顺序，其它一些实现（比如HashMap）则不保证元素在其内部有序。&lt;/p&gt;
        &lt;/blockquote&gt;
      &lt;/li&gt;
    &lt;/ul&gt;
  &lt;/li&gt;
  &lt;li&gt;HashMap
    &lt;ul&gt;
      &lt;li&gt;定义
        &lt;blockquote&gt;
          &lt;p&gt;HashMap&amp;lt;K, V&amp;gt;是基于哈希表这个数据结构的Map接口具体实现，允许null键和null值（最多只允许一个key为null，但允许多个value为null）。这个类与HashTable近似等价，区别在于HashMap不是线程安全的并且允许null键和null值。由于基于哈希表实现，所以HashMap内部的元素是无序的。HashMap对与get与put操作的时间复杂度是常数级别的（在散列均匀的前提下）。对HashMap的集合视图进行迭代所需时间与HashMap的capacity（bucket的数量）加上HashMap的尺寸（键值对的数量）成正比。因此，若迭代操作的性能很重要，不要把初始capacity设的过高（不要把load factor设的过低）。&lt;/p&gt;
        &lt;/blockquote&gt;
      &lt;/li&gt;
    &lt;/ul&gt;
  &lt;/li&gt;
&lt;/ol&gt;

&lt;ul&gt;
  &lt;li&gt;影响性能的因素：
    &lt;ul&gt;
      &lt;li&gt;intial capacity（初始容量）：HashMap对象刚创建时其内部的哈希表的“桶”的数量；&lt;/li&gt;
      &lt;li&gt;load factor（负载因子）：maxSize / capacity，也就是HashMap所允许的最大键值对数与桶数的比值，当我们清楚自己将要大概存放多少数据时，也可以自定义load factor的大小；
&lt;em&gt;注意：增大load factor可以节省空间但查找一个元素的时间会增加，减小load factor会占用更多的存储空间，但是get与put的操作会更快。当HashMap中的键值对数量超过了maxSize（即load factor与capacity的乘积），它会再散列，再散列会重建内部数据结构，桶数（capacity）大约会增加到原来的两倍。&lt;/em&gt;&lt;/li&gt;
    &lt;/ul&gt;
  &lt;/li&gt;
&lt;/ul&gt;

&lt;div class=&quot;language-java highlighter-rouge&quot;&gt;&lt;pre class=&quot;highlight&quot;&gt;&lt;code&gt;&lt;span class=&quot;c1&quot;&gt;//默认初始容量是16，必须是2的幂  &lt;/span&gt;
&lt;span class=&quot;kd&quot;&gt;static&lt;/span&gt; &lt;span class=&quot;kd&quot;&gt;final&lt;/span&gt; &lt;span class=&quot;kt&quot;&gt;int&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;DEFAULT_INITIAL_CAPACITY&lt;/span&gt; &lt;span class=&quot;o&quot;&gt;=&lt;/span&gt; &lt;span class=&quot;mi&quot;&gt;1&lt;/span&gt; &lt;span class=&quot;o&quot;&gt;&amp;lt;&amp;lt;&lt;/span&gt; &lt;span class=&quot;mi&quot;&gt;4&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;;&lt;/span&gt; &lt;span class=&quot;c1&quot;&gt;// aka 16  &lt;/span&gt;

&lt;span class=&quot;c1&quot;&gt;//最大容量（必须是2的幂且小于2的30次方，传入容量过大会被这个值替换）  &lt;/span&gt;
&lt;span class=&quot;kd&quot;&gt;static&lt;/span&gt; &lt;span class=&quot;kd&quot;&gt;final&lt;/span&gt; &lt;span class=&quot;kt&quot;&gt;int&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;MAXIMUM_CAPACITY&lt;/span&gt; &lt;span class=&quot;o&quot;&gt;=&lt;/span&gt; &lt;span class=&quot;mi&quot;&gt;1&lt;/span&gt; &lt;span class=&quot;o&quot;&gt;&amp;lt;&amp;lt;&lt;/span&gt; &lt;span class=&quot;mi&quot;&gt;30&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;;&lt;/span&gt;  

&lt;span class=&quot;c1&quot;&gt;//默认加载因子，所谓加载因子是指哈希表在其容量自动增加之前可以达到多满的一种尺度  &lt;/span&gt;
&lt;span class=&quot;kd&quot;&gt;static&lt;/span&gt; &lt;span class=&quot;kd&quot;&gt;final&lt;/span&gt; &lt;span class=&quot;kt&quot;&gt;float&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;DEFAULT_LOAD_FACTOR&lt;/span&gt; &lt;span class=&quot;o&quot;&gt;=&lt;/span&gt; &lt;span class=&quot;mf&quot;&gt;0.75f&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;;&lt;/span&gt;  

&lt;span class=&quot;c1&quot;&gt;//存储Entry的默认空数组  &lt;/span&gt;
&lt;span class=&quot;kd&quot;&gt;static&lt;/span&gt; &lt;span class=&quot;kd&quot;&gt;final&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;Entry&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;&amp;lt;?,?&amp;gt;[]&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;EMPTY_TABLE&lt;/span&gt; &lt;span class=&quot;o&quot;&gt;=&lt;/span&gt; &lt;span class=&quot;o&quot;&gt;{};&lt;/span&gt;  

&lt;span class=&quot;c1&quot;&gt;//存储Entry的数组，长度为2的幂。HashMap采用拉链法实现的，每个Entry的本质是个单向链表  &lt;/span&gt;
&lt;span class=&quot;kd&quot;&gt;transient&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;Entry&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;&amp;lt;&lt;/span&gt;&lt;span class=&quot;n&quot;&gt;K&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;,&lt;/span&gt;&lt;span class=&quot;n&quot;&gt;V&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;&amp;gt;[]&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;table&lt;/span&gt; &lt;span class=&quot;o&quot;&gt;=&lt;/span&gt; &lt;span class=&quot;o&quot;&gt;(&lt;/span&gt;&lt;span class=&quot;n&quot;&gt;Entry&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;&amp;lt;&lt;/span&gt;&lt;span class=&quot;n&quot;&gt;K&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;,&lt;/span&gt;&lt;span class=&quot;n&quot;&gt;V&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;&amp;gt;[])&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;EMPTY_TABLE&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;;&lt;/span&gt;  

&lt;span class=&quot;c1&quot;&gt;//HashMap的大小，即HashMap存储的键值对数量  &lt;/span&gt;
&lt;span class=&quot;kd&quot;&gt;transient&lt;/span&gt; &lt;span class=&quot;kt&quot;&gt;int&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;size&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;;&lt;/span&gt;  

&lt;span class=&quot;c1&quot;&gt;//HashMap的阈值，用于判断是否需要调整HashMap的容量  &lt;/span&gt;
&lt;span class=&quot;kt&quot;&gt;int&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;threshold&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;;&lt;/span&gt;  

&lt;span class=&quot;c1&quot;&gt;//加载因子实际大小  &lt;/span&gt;
&lt;span class=&quot;kd&quot;&gt;final&lt;/span&gt; &lt;span class=&quot;kt&quot;&gt;float&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;loadFactor&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;;&lt;/span&gt;  

&lt;span class=&quot;c1&quot;&gt;//HashMap被修改的次数，用于fail-fast机制  &lt;/span&gt;
&lt;span class=&quot;kd&quot;&gt;transient&lt;/span&gt; &lt;span class=&quot;kt&quot;&gt;int&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;modCount&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;;&lt;/span&gt;
&lt;/code&gt;&lt;/pre&gt;
&lt;/div&gt;

&lt;ul&gt;
  &lt;li&gt;
    &lt;p&gt;HashMap构造函数&lt;/p&gt;

    &lt;div class=&quot;language-java highlighter-rouge&quot;&gt;&lt;pre class=&quot;highlight&quot;&gt;&lt;code&gt;&lt;span class=&quot;cm&quot;&gt;/**
     * Constructs an empty &amp;lt;tt&amp;gt;HashMap&amp;lt;/tt&amp;gt; with the specified initial
     * capacity and load factor.
     *
     * @param  initialCapacity the initial capacity
     * @param  loadFactor      the load factor
     * @throws IllegalArgumentException if the initial capacity is negative
     *         or the load factor is nonpositive
     */&lt;/span&gt;
    &lt;span class=&quot;kd&quot;&gt;public&lt;/span&gt; &lt;span class=&quot;nf&quot;&gt;HashMap&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;(&lt;/span&gt;&lt;span class=&quot;kt&quot;&gt;int&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;initialCapacity&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;,&lt;/span&gt; &lt;span class=&quot;kt&quot;&gt;float&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;loadFactor&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;)&lt;/span&gt; &lt;span class=&quot;o&quot;&gt;{&lt;/span&gt;
        &lt;span class=&quot;k&quot;&gt;if&lt;/span&gt; &lt;span class=&quot;o&quot;&gt;(&lt;/span&gt;&lt;span class=&quot;n&quot;&gt;initialCapacity&lt;/span&gt; &lt;span class=&quot;o&quot;&gt;&amp;lt;&lt;/span&gt; &lt;span class=&quot;mi&quot;&gt;0&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;)&lt;/span&gt;
            &lt;span class=&quot;k&quot;&gt;throw&lt;/span&gt; &lt;span class=&quot;k&quot;&gt;new&lt;/span&gt; &lt;span class=&quot;nf&quot;&gt;IllegalArgumentException&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;(&lt;/span&gt;&lt;span class=&quot;s&quot;&gt;&quot;Illegal initial capacity: &quot;&lt;/span&gt; &lt;span class=&quot;o&quot;&gt;+&lt;/span&gt;
                                               &lt;span class=&quot;n&quot;&gt;initialCapacity&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;);&lt;/span&gt;
        &lt;span class=&quot;k&quot;&gt;if&lt;/span&gt; &lt;span class=&quot;o&quot;&gt;(&lt;/span&gt;&lt;span class=&quot;n&quot;&gt;initialCapacity&lt;/span&gt; &lt;span class=&quot;o&quot;&gt;&amp;gt;&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;MAXIMUM_CAPACITY&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;)&lt;/span&gt;
            &lt;span class=&quot;n&quot;&gt;initialCapacity&lt;/span&gt; &lt;span class=&quot;o&quot;&gt;=&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;MAXIMUM_CAPACITY&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;;&lt;/span&gt;
        &lt;span class=&quot;k&quot;&gt;if&lt;/span&gt; &lt;span class=&quot;o&quot;&gt;(&lt;/span&gt;&lt;span class=&quot;n&quot;&gt;loadFactor&lt;/span&gt; &lt;span class=&quot;o&quot;&gt;&amp;lt;=&lt;/span&gt; &lt;span class=&quot;mi&quot;&gt;0&lt;/span&gt; &lt;span class=&quot;o&quot;&gt;||&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;Float&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;.&lt;/span&gt;&lt;span class=&quot;na&quot;&gt;isNaN&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;(&lt;/span&gt;&lt;span class=&quot;n&quot;&gt;loadFactor&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;))&lt;/span&gt;
            &lt;span class=&quot;k&quot;&gt;throw&lt;/span&gt; &lt;span class=&quot;k&quot;&gt;new&lt;/span&gt; &lt;span class=&quot;nf&quot;&gt;IllegalArgumentException&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;(&lt;/span&gt;&lt;span class=&quot;s&quot;&gt;&quot;Illegal load factor: &quot;&lt;/span&gt; &lt;span class=&quot;o&quot;&gt;+&lt;/span&gt;
                                               &lt;span class=&quot;n&quot;&gt;loadFactor&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;);&lt;/span&gt;

        &lt;span class=&quot;k&quot;&gt;this&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;.&lt;/span&gt;&lt;span class=&quot;na&quot;&gt;loadFactor&lt;/span&gt; &lt;span class=&quot;o&quot;&gt;=&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;loadFactor&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;;&lt;/span&gt;
        &lt;span class=&quot;n&quot;&gt;threshold&lt;/span&gt; &lt;span class=&quot;o&quot;&gt;=&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;initialCapacity&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;;&lt;/span&gt;
        &lt;span class=&quot;n&quot;&gt;init&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;();&lt;/span&gt;
    &lt;span class=&quot;o&quot;&gt;}&lt;/span&gt;
&lt;/code&gt;&lt;/pre&gt;
    &lt;/div&gt;
    &lt;p&gt;&lt;code class=&quot;highlighter-rouge&quot;&gt;threshold&lt;/code&gt;即为上文提到的maxSize。&lt;/p&gt;
  &lt;/li&gt;
  &lt;li&gt;
    &lt;p&gt;基本实现原理
  HashMap是基于拉链法处理碰撞的散列表的实现，一个存储整型元素的HashMap的内部存储结构如下图所示：&lt;/p&gt;
  &lt;/li&gt;
&lt;/ul&gt;
&lt;figure&gt;
  	&lt;img src=&quot;http://upload-images.jianshu.io/upload_images/2397836-3be8c0d8ef3f12bf.png?imageMogr2/auto-orient/strip%7CimageView2/2/w/1240&quot; /&gt;
  &lt;/figure&gt;
&lt;p&gt;我们可以看到，HashMap是采用&lt;code class=&quot;highlighter-rouge&quot;&gt;数组+链表&lt;/code&gt;实现的，&lt;strong&gt;在JDK 1.8中，对HashMap做了进一步优化，引入了红黑树。当链表的长度大于8时，就会使用红黑树来代替链表&lt;/strong&gt;。&lt;/p&gt;

&lt;ul&gt;
  &lt;li&gt;源码分析
    &lt;ul&gt;
      &lt;li&gt;jdk1.7
        &lt;ul&gt;
          &lt;li&gt;&lt;code class=&quot;highlighter-rouge&quot;&gt;table&lt;/code&gt;字段是一个Entry&amp;lt;K, V&amp;gt;数组.&lt;/li&gt;
          &lt;li&gt;HashMap的底层是通过链表来解决&lt;code class=&quot;highlighter-rouge&quot;&gt;hash冲突&lt;/code&gt;的，即&lt;code class=&quot;highlighter-rouge&quot;&gt;碰撞&lt;/code&gt;.&lt;/li&gt;
        &lt;/ul&gt;

        &lt;div class=&quot;language-java highlighter-rouge&quot;&gt;&lt;pre class=&quot;highlight&quot;&gt;&lt;code&gt;  &lt;span class=&quot;cm&quot;&gt;/**
    * An empty table instance to share when the table is not inflated.
    */&lt;/span&gt;
   &lt;span class=&quot;kd&quot;&gt;static&lt;/span&gt; &lt;span class=&quot;kd&quot;&gt;final&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;Entry&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;&amp;lt;?,?&amp;gt;[]&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;EMPTY_TABLE&lt;/span&gt; &lt;span class=&quot;o&quot;&gt;=&lt;/span&gt; &lt;span class=&quot;o&quot;&gt;{};&lt;/span&gt;

   &lt;span class=&quot;cm&quot;&gt;/**
    * The table, resized as necessary. Length MUST Always be a power of two.
    */&lt;/span&gt;
   &lt;span class=&quot;kd&quot;&gt;transient&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;Entry&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;&amp;lt;&lt;/span&gt;&lt;span class=&quot;n&quot;&gt;K&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;,&lt;/span&gt;&lt;span class=&quot;n&quot;&gt;V&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;&amp;gt;[]&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;table&lt;/span&gt; &lt;span class=&quot;o&quot;&gt;=&lt;/span&gt; &lt;span class=&quot;o&quot;&gt;(&lt;/span&gt;&lt;span class=&quot;n&quot;&gt;Entry&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;&amp;lt;&lt;/span&gt;&lt;span class=&quot;n&quot;&gt;K&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;,&lt;/span&gt;&lt;span class=&quot;n&quot;&gt;V&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;&amp;gt;[])&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;EMPTY_TABLE&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;;&lt;/span&gt;

   &lt;span class=&quot;cm&quot;&gt;/**
    * Entry&amp;lt;K,V&amp;gt;是存储对应键值对的节点，里面还定义了next指向了下一个节点
    * 所以是一个单向链表，是HashMap链式存储对应的链表
    *
    */&lt;/span&gt;
   &lt;span class=&quot;kd&quot;&gt;static&lt;/span&gt; &lt;span class=&quot;kd&quot;&gt;class&lt;/span&gt; &lt;span class=&quot;nc&quot;&gt;Entry&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;&amp;lt;&lt;/span&gt;&lt;span class=&quot;n&quot;&gt;K&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;,&lt;/span&gt;&lt;span class=&quot;n&quot;&gt;V&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;&amp;gt;&lt;/span&gt; &lt;span class=&quot;kd&quot;&gt;implements&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;Map&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;.&lt;/span&gt;&lt;span class=&quot;na&quot;&gt;Entry&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;&amp;lt;&lt;/span&gt;&lt;span class=&quot;n&quot;&gt;K&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;,&lt;/span&gt;&lt;span class=&quot;n&quot;&gt;V&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;&amp;gt;&lt;/span&gt; &lt;span class=&quot;o&quot;&gt;{&lt;/span&gt;
     &lt;span class=&quot;kd&quot;&gt;final&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;K&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;key&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;;&lt;/span&gt;
     &lt;span class=&quot;n&quot;&gt;V&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;value&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;;&lt;/span&gt;
     &lt;span class=&quot;n&quot;&gt;Entry&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;&amp;lt;&lt;/span&gt;&lt;span class=&quot;n&quot;&gt;K&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;,&lt;/span&gt;&lt;span class=&quot;n&quot;&gt;V&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;&amp;gt;&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;next&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;;&lt;/span&gt;
     &lt;span class=&quot;kt&quot;&gt;int&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;hash&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;;&lt;/span&gt;
     &lt;span class=&quot;cm&quot;&gt;/**
      * Creates new entry.
      */&lt;/span&gt;
     &lt;span class=&quot;n&quot;&gt;Entry&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;(&lt;/span&gt;&lt;span class=&quot;kt&quot;&gt;int&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;h&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;,&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;K&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;k&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;,&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;V&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;v&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;,&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;Entry&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;&amp;lt;&lt;/span&gt;&lt;span class=&quot;n&quot;&gt;K&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;,&lt;/span&gt;&lt;span class=&quot;n&quot;&gt;V&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;&amp;gt;&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;n&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;)&lt;/span&gt; &lt;span class=&quot;o&quot;&gt;{&lt;/span&gt;
         &lt;span class=&quot;n&quot;&gt;value&lt;/span&gt; &lt;span class=&quot;o&quot;&gt;=&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;v&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;;&lt;/span&gt;
         &lt;span class=&quot;n&quot;&gt;next&lt;/span&gt; &lt;span class=&quot;o&quot;&gt;=&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;n&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;;&lt;/span&gt;
         &lt;span class=&quot;n&quot;&gt;key&lt;/span&gt; &lt;span class=&quot;o&quot;&gt;=&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;k&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;;&lt;/span&gt;
         &lt;span class=&quot;n&quot;&gt;hash&lt;/span&gt; &lt;span class=&quot;o&quot;&gt;=&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;h&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;;&lt;/span&gt;
     &lt;span class=&quot;o&quot;&gt;}&lt;/span&gt;
     &lt;span class=&quot;kd&quot;&gt;public&lt;/span&gt; &lt;span class=&quot;kd&quot;&gt;final&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;K&lt;/span&gt; &lt;span class=&quot;nf&quot;&gt;getKey&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;()&lt;/span&gt; &lt;span class=&quot;o&quot;&gt;{&lt;/span&gt;
         &lt;span class=&quot;k&quot;&gt;return&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;key&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;;&lt;/span&gt;
     &lt;span class=&quot;o&quot;&gt;}&lt;/span&gt;
     &lt;span class=&quot;kd&quot;&gt;public&lt;/span&gt; &lt;span class=&quot;kd&quot;&gt;final&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;V&lt;/span&gt; &lt;span class=&quot;nf&quot;&gt;getValue&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;()&lt;/span&gt; &lt;span class=&quot;o&quot;&gt;{&lt;/span&gt;
         &lt;span class=&quot;k&quot;&gt;return&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;value&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;;&lt;/span&gt;
     &lt;span class=&quot;o&quot;&gt;}&lt;/span&gt;
     &lt;span class=&quot;kd&quot;&gt;public&lt;/span&gt; &lt;span class=&quot;kd&quot;&gt;final&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;V&lt;/span&gt; &lt;span class=&quot;nf&quot;&gt;setValue&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;(&lt;/span&gt;&lt;span class=&quot;n&quot;&gt;V&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;newValue&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;)&lt;/span&gt; &lt;span class=&quot;o&quot;&gt;{&lt;/span&gt;
         &lt;span class=&quot;n&quot;&gt;V&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;oldValue&lt;/span&gt; &lt;span class=&quot;o&quot;&gt;=&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;value&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;;&lt;/span&gt;
         &lt;span class=&quot;n&quot;&gt;value&lt;/span&gt; &lt;span class=&quot;o&quot;&gt;=&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;newValue&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;;&lt;/span&gt;
         &lt;span class=&quot;k&quot;&gt;return&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;oldValue&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;;&lt;/span&gt;
     &lt;span class=&quot;o&quot;&gt;}&lt;/span&gt;
     &lt;span class=&quot;c1&quot;&gt;//重写了equals方法，用于遍历链表取值&lt;/span&gt;
     &lt;span class=&quot;kd&quot;&gt;public&lt;/span&gt; &lt;span class=&quot;kd&quot;&gt;final&lt;/span&gt; &lt;span class=&quot;kt&quot;&gt;boolean&lt;/span&gt; &lt;span class=&quot;nf&quot;&gt;equals&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;(&lt;/span&gt;&lt;span class=&quot;n&quot;&gt;Object&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;o&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;)&lt;/span&gt; &lt;span class=&quot;o&quot;&gt;{&lt;/span&gt;
         &lt;span class=&quot;k&quot;&gt;if&lt;/span&gt; &lt;span class=&quot;o&quot;&gt;(!(&lt;/span&gt;&lt;span class=&quot;n&quot;&gt;o&lt;/span&gt; &lt;span class=&quot;k&quot;&gt;instanceof&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;Map&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;.&lt;/span&gt;&lt;span class=&quot;na&quot;&gt;Entry&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;))&lt;/span&gt;
             &lt;span class=&quot;k&quot;&gt;return&lt;/span&gt; &lt;span class=&quot;kc&quot;&gt;false&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;;&lt;/span&gt;
         &lt;span class=&quot;n&quot;&gt;Map&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;.&lt;/span&gt;&lt;span class=&quot;na&quot;&gt;Entry&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;e&lt;/span&gt; &lt;span class=&quot;o&quot;&gt;=&lt;/span&gt; &lt;span class=&quot;o&quot;&gt;(&lt;/span&gt;&lt;span class=&quot;n&quot;&gt;Map&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;.&lt;/span&gt;&lt;span class=&quot;na&quot;&gt;Entry&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;)&lt;/span&gt;&lt;span class=&quot;n&quot;&gt;o&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;;&lt;/span&gt;
         &lt;span class=&quot;n&quot;&gt;Object&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;k1&lt;/span&gt; &lt;span class=&quot;o&quot;&gt;=&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;getKey&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;();&lt;/span&gt;
         &lt;span class=&quot;n&quot;&gt;Object&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;k2&lt;/span&gt; &lt;span class=&quot;o&quot;&gt;=&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;e&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;.&lt;/span&gt;&lt;span class=&quot;na&quot;&gt;getKey&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;();&lt;/span&gt;
         &lt;span class=&quot;k&quot;&gt;if&lt;/span&gt; &lt;span class=&quot;o&quot;&gt;(&lt;/span&gt;&lt;span class=&quot;n&quot;&gt;k1&lt;/span&gt; &lt;span class=&quot;o&quot;&gt;==&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;k2&lt;/span&gt; &lt;span class=&quot;o&quot;&gt;||&lt;/span&gt; &lt;span class=&quot;o&quot;&gt;(&lt;/span&gt;&lt;span class=&quot;n&quot;&gt;k1&lt;/span&gt; &lt;span class=&quot;o&quot;&gt;!=&lt;/span&gt; &lt;span class=&quot;kc&quot;&gt;null&lt;/span&gt; &lt;span class=&quot;o&quot;&gt;&amp;amp;&amp;amp;&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;k1&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;.&lt;/span&gt;&lt;span class=&quot;na&quot;&gt;equals&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;(&lt;/span&gt;&lt;span class=&quot;n&quot;&gt;k2&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;)))&lt;/span&gt; &lt;span class=&quot;o&quot;&gt;{&lt;/span&gt;
             &lt;span class=&quot;n&quot;&gt;Object&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;v1&lt;/span&gt; &lt;span class=&quot;o&quot;&gt;=&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;getValue&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;();&lt;/span&gt;
             &lt;span class=&quot;n&quot;&gt;Object&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;v2&lt;/span&gt; &lt;span class=&quot;o&quot;&gt;=&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;e&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;.&lt;/span&gt;&lt;span class=&quot;na&quot;&gt;getValue&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;();&lt;/span&gt;
             &lt;span class=&quot;k&quot;&gt;if&lt;/span&gt; &lt;span class=&quot;o&quot;&gt;(&lt;/span&gt;&lt;span class=&quot;n&quot;&gt;v1&lt;/span&gt; &lt;span class=&quot;o&quot;&gt;==&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;v2&lt;/span&gt; &lt;span class=&quot;o&quot;&gt;||&lt;/span&gt; &lt;span class=&quot;o&quot;&gt;(&lt;/span&gt;&lt;span class=&quot;n&quot;&gt;v1&lt;/span&gt; &lt;span class=&quot;o&quot;&gt;!=&lt;/span&gt; &lt;span class=&quot;kc&quot;&gt;null&lt;/span&gt; &lt;span class=&quot;o&quot;&gt;&amp;amp;&amp;amp;&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;v1&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;.&lt;/span&gt;&lt;span class=&quot;na&quot;&gt;equals&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;(&lt;/span&gt;&lt;span class=&quot;n&quot;&gt;v2&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;)))&lt;/span&gt;
                 &lt;span class=&quot;k&quot;&gt;return&lt;/span&gt; &lt;span class=&quot;kc&quot;&gt;true&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;;&lt;/span&gt;
         &lt;span class=&quot;o&quot;&gt;}&lt;/span&gt;
         &lt;span class=&quot;k&quot;&gt;return&lt;/span&gt; &lt;span class=&quot;kc&quot;&gt;false&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;;&lt;/span&gt;
     &lt;span class=&quot;o&quot;&gt;}&lt;/span&gt;
     &lt;span class=&quot;kd&quot;&gt;public&lt;/span&gt; &lt;span class=&quot;kd&quot;&gt;final&lt;/span&gt; &lt;span class=&quot;kt&quot;&gt;int&lt;/span&gt; &lt;span class=&quot;nf&quot;&gt;hashCode&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;()&lt;/span&gt; &lt;span class=&quot;o&quot;&gt;{&lt;/span&gt;
         &lt;span class=&quot;k&quot;&gt;return&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;Objects&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;.&lt;/span&gt;&lt;span class=&quot;na&quot;&gt;hashCode&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;(&lt;/span&gt;&lt;span class=&quot;n&quot;&gt;getKey&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;())&lt;/span&gt; &lt;span class=&quot;o&quot;&gt;^&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;Objects&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;.&lt;/span&gt;&lt;span class=&quot;na&quot;&gt;hashCode&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;(&lt;/span&gt;&lt;span class=&quot;n&quot;&gt;getValue&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;());&lt;/span&gt;
     &lt;span class=&quot;o&quot;&gt;}&lt;/span&gt;

     &lt;span class=&quot;kd&quot;&gt;public&lt;/span&gt; &lt;span class=&quot;kd&quot;&gt;final&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;String&lt;/span&gt; &lt;span class=&quot;nf&quot;&gt;toString&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;()&lt;/span&gt; &lt;span class=&quot;o&quot;&gt;{&lt;/span&gt;
         &lt;span class=&quot;k&quot;&gt;return&lt;/span&gt; &lt;span class=&quot;nf&quot;&gt;getKey&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;()&lt;/span&gt; &lt;span class=&quot;o&quot;&gt;+&lt;/span&gt; &lt;span class=&quot;s&quot;&gt;&quot;=&quot;&lt;/span&gt; &lt;span class=&quot;o&quot;&gt;+&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;getValue&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;();&lt;/span&gt;
     &lt;span class=&quot;o&quot;&gt;}&lt;/span&gt;
     &lt;span class=&quot;cm&quot;&gt;/**
      * 当向HashMap中添加元素时，即调用put(k,v)时，
      * 对已经在HashMap中k位置进行v的覆盖时，会调用此方法
      * 这里没做任何处理
      */&lt;/span&gt;  
     &lt;span class=&quot;kt&quot;&gt;void&lt;/span&gt; &lt;span class=&quot;nf&quot;&gt;recordAccess&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;(&lt;/span&gt;&lt;span class=&quot;n&quot;&gt;HashMap&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;&amp;lt;&lt;/span&gt;&lt;span class=&quot;n&quot;&gt;K&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;,&lt;/span&gt;&lt;span class=&quot;n&quot;&gt;V&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;&amp;gt;&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;m&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;)&lt;/span&gt; &lt;span class=&quot;o&quot;&gt;{&lt;/span&gt;
     &lt;span class=&quot;o&quot;&gt;}&lt;/span&gt;
     &lt;span class=&quot;cm&quot;&gt;/**
      * 当从HashMap中删除了一个Entry时，会调用该函数
      * 这里没做任何处理
      */&lt;/span&gt;  
     &lt;span class=&quot;kt&quot;&gt;void&lt;/span&gt; &lt;span class=&quot;nf&quot;&gt;recordRemoval&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;(&lt;/span&gt;&lt;span class=&quot;n&quot;&gt;HashMap&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;&amp;lt;&lt;/span&gt;&lt;span class=&quot;n&quot;&gt;K&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;,&lt;/span&gt;&lt;span class=&quot;n&quot;&gt;V&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;&amp;gt;&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;m&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;)&lt;/span&gt; &lt;span class=&quot;o&quot;&gt;{&lt;/span&gt;
     &lt;span class=&quot;o&quot;&gt;}&lt;/span&gt;
 &lt;span class=&quot;o&quot;&gt;}&lt;/span&gt;
 &lt;span class=&quot;cm&quot;&gt;/**
 * Associates the specified value with the specified key in this map.
 * If the map previously contained a mapping for the key, the old
 * value is replaced.
 *
 * @param key key with which the specified value is to be associated
 * @param value value to be associated with the specified key
 * @return the previous value associated with &amp;lt;tt&amp;gt;key&amp;lt;/tt&amp;gt;, or
 *         &amp;lt;tt&amp;gt;null&amp;lt;/tt&amp;gt; if there was no mapping for &amp;lt;tt&amp;gt;key&amp;lt;/tt&amp;gt;.
 *         (A &amp;lt;tt&amp;gt;null&amp;lt;/tt&amp;gt; return can also indicate that the map
 *         previously associated &amp;lt;tt&amp;gt;null&amp;lt;/tt&amp;gt; with &amp;lt;tt&amp;gt;key&amp;lt;/tt&amp;gt;.)
 */&lt;/span&gt;
&lt;span class=&quot;kd&quot;&gt;public&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;V&lt;/span&gt; &lt;span class=&quot;nf&quot;&gt;put&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;(&lt;/span&gt;&lt;span class=&quot;n&quot;&gt;K&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;key&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;,&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;V&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;value&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;)&lt;/span&gt; &lt;span class=&quot;o&quot;&gt;{&lt;/span&gt;
    &lt;span class=&quot;c1&quot;&gt;//如果哈希表没有初始化(table为空)  &lt;/span&gt;
    &lt;span class=&quot;c1&quot;&gt;//用构造时的阈值(其实就是初始容量)扩展table  &lt;/span&gt;
    &lt;span class=&quot;k&quot;&gt;if&lt;/span&gt; &lt;span class=&quot;o&quot;&gt;(&lt;/span&gt;&lt;span class=&quot;n&quot;&gt;table&lt;/span&gt; &lt;span class=&quot;o&quot;&gt;==&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;EMPTY_TABLE&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;)&lt;/span&gt; &lt;span class=&quot;o&quot;&gt;{&lt;/span&gt;
        &lt;span class=&quot;n&quot;&gt;inflateTable&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;(&lt;/span&gt;&lt;span class=&quot;n&quot;&gt;threshold&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;);&lt;/span&gt;
    &lt;span class=&quot;o&quot;&gt;}&lt;/span&gt;
    &lt;span class=&quot;k&quot;&gt;if&lt;/span&gt; &lt;span class=&quot;o&quot;&gt;(&lt;/span&gt;&lt;span class=&quot;n&quot;&gt;key&lt;/span&gt; &lt;span class=&quot;o&quot;&gt;==&lt;/span&gt; &lt;span class=&quot;kc&quot;&gt;null&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;)&lt;/span&gt;
    &lt;span class=&quot;c1&quot;&gt;//如果key==null，就将value加到table[0]的位置  &lt;/span&gt;
    &lt;span class=&quot;c1&quot;&gt;//该位置永远只有一个value，新传进来的value会覆盖旧的value   &lt;/span&gt;
        &lt;span class=&quot;k&quot;&gt;return&lt;/span&gt; &lt;span class=&quot;nf&quot;&gt;putForNullKey&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;(&lt;/span&gt;&lt;span class=&quot;n&quot;&gt;value&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;);&lt;/span&gt;
    &lt;span class=&quot;c1&quot;&gt;//计算hash值，并且计算出值的索引&lt;/span&gt;
    &lt;span class=&quot;kt&quot;&gt;int&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;hash&lt;/span&gt; &lt;span class=&quot;o&quot;&gt;=&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;hash&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;(&lt;/span&gt;&lt;span class=&quot;n&quot;&gt;key&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;);&lt;/span&gt;
    &lt;span class=&quot;kt&quot;&gt;int&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;i&lt;/span&gt; &lt;span class=&quot;o&quot;&gt;=&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;indexFor&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;(&lt;/span&gt;&lt;span class=&quot;n&quot;&gt;hash&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;,&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;table&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;.&lt;/span&gt;&lt;span class=&quot;na&quot;&gt;length&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;);&lt;/span&gt;
    &lt;span class=&quot;k&quot;&gt;for&lt;/span&gt; &lt;span class=&quot;o&quot;&gt;(&lt;/span&gt;&lt;span class=&quot;n&quot;&gt;Entry&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;&amp;lt;&lt;/span&gt;&lt;span class=&quot;n&quot;&gt;K&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;,&lt;/span&gt;&lt;span class=&quot;n&quot;&gt;V&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;&amp;gt;&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;e&lt;/span&gt; &lt;span class=&quot;o&quot;&gt;=&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;table&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;[&lt;/span&gt;&lt;span class=&quot;n&quot;&gt;i&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;];&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;e&lt;/span&gt; &lt;span class=&quot;o&quot;&gt;!=&lt;/span&gt; &lt;span class=&quot;kc&quot;&gt;null&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;;&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;e&lt;/span&gt; &lt;span class=&quot;o&quot;&gt;=&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;e&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;.&lt;/span&gt;&lt;span class=&quot;na&quot;&gt;next&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;)&lt;/span&gt; &lt;span class=&quot;o&quot;&gt;{&lt;/span&gt;
        &lt;span class=&quot;n&quot;&gt;Object&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;k&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;;&lt;/span&gt;
        &lt;span class=&quot;k&quot;&gt;if&lt;/span&gt; &lt;span class=&quot;o&quot;&gt;(&lt;/span&gt;&lt;span class=&quot;n&quot;&gt;e&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;.&lt;/span&gt;&lt;span class=&quot;na&quot;&gt;hash&lt;/span&gt; &lt;span class=&quot;o&quot;&gt;==&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;hash&lt;/span&gt; &lt;span class=&quot;o&quot;&gt;&amp;amp;&amp;amp;&lt;/span&gt; &lt;span class=&quot;o&quot;&gt;((&lt;/span&gt;&lt;span class=&quot;n&quot;&gt;k&lt;/span&gt; &lt;span class=&quot;o&quot;&gt;=&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;e&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;.&lt;/span&gt;&lt;span class=&quot;na&quot;&gt;key&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;)&lt;/span&gt; &lt;span class=&quot;o&quot;&gt;==&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;key&lt;/span&gt; &lt;span class=&quot;o&quot;&gt;||&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;key&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;.&lt;/span&gt;&lt;span class=&quot;na&quot;&gt;equals&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;(&lt;/span&gt;&lt;span class=&quot;n&quot;&gt;k&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;)))&lt;/span&gt; &lt;span class=&quot;o&quot;&gt;{&lt;/span&gt;
            &lt;span class=&quot;n&quot;&gt;V&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;oldValue&lt;/span&gt; &lt;span class=&quot;o&quot;&gt;=&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;e&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;.&lt;/span&gt;&lt;span class=&quot;na&quot;&gt;value&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;;&lt;/span&gt;
            &lt;span class=&quot;n&quot;&gt;e&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;.&lt;/span&gt;&lt;span class=&quot;na&quot;&gt;value&lt;/span&gt; &lt;span class=&quot;o&quot;&gt;=&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;value&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;;&lt;/span&gt;
            &lt;span class=&quot;n&quot;&gt;e&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;.&lt;/span&gt;&lt;span class=&quot;na&quot;&gt;recordAccess&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;(&lt;/span&gt;&lt;span class=&quot;k&quot;&gt;this&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;);&lt;/span&gt;
            &lt;span class=&quot;k&quot;&gt;return&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;oldValue&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;;&lt;/span&gt;
        &lt;span class=&quot;o&quot;&gt;}&lt;/span&gt;
    &lt;span class=&quot;o&quot;&gt;}&lt;/span&gt;
    &lt;span class=&quot;n&quot;&gt;modCount&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;++;&lt;/span&gt;
    &lt;span class=&quot;c1&quot;&gt;//如果在table[i]中没找到对应的key，那么就直接在该位置的链表中添加此Entry&lt;/span&gt;
    &lt;span class=&quot;n&quot;&gt;addEntry&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;(&lt;/span&gt;&lt;span class=&quot;n&quot;&gt;hash&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;,&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;key&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;,&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;value&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;,&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;i&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;);&lt;/span&gt;
    &lt;span class=&quot;k&quot;&gt;return&lt;/span&gt; &lt;span class=&quot;kc&quot;&gt;null&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;;&lt;/span&gt;
&lt;span class=&quot;o&quot;&gt;}&lt;/span&gt;
&lt;span class=&quot;cm&quot;&gt;/**
 * Offloaded version of put for null keys
 */&lt;/span&gt;
&lt;span class=&quot;kd&quot;&gt;private&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;V&lt;/span&gt; &lt;span class=&quot;nf&quot;&gt;putForNullKey&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;(&lt;/span&gt;&lt;span class=&quot;n&quot;&gt;V&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;value&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;)&lt;/span&gt; &lt;span class=&quot;o&quot;&gt;{&lt;/span&gt;
    &lt;span class=&quot;k&quot;&gt;for&lt;/span&gt; &lt;span class=&quot;o&quot;&gt;(&lt;/span&gt;&lt;span class=&quot;n&quot;&gt;Entry&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;&amp;lt;&lt;/span&gt;&lt;span class=&quot;n&quot;&gt;K&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;,&lt;/span&gt;&lt;span class=&quot;n&quot;&gt;V&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;&amp;gt;&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;e&lt;/span&gt; &lt;span class=&quot;o&quot;&gt;=&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;table&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;[&lt;/span&gt;&lt;span class=&quot;mi&quot;&gt;0&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;];&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;e&lt;/span&gt; &lt;span class=&quot;o&quot;&gt;!=&lt;/span&gt; &lt;span class=&quot;kc&quot;&gt;null&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;;&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;e&lt;/span&gt; &lt;span class=&quot;o&quot;&gt;=&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;e&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;.&lt;/span&gt;&lt;span class=&quot;na&quot;&gt;next&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;)&lt;/span&gt; &lt;span class=&quot;o&quot;&gt;{&lt;/span&gt;
        &lt;span class=&quot;k&quot;&gt;if&lt;/span&gt; &lt;span class=&quot;o&quot;&gt;(&lt;/span&gt;&lt;span class=&quot;n&quot;&gt;e&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;.&lt;/span&gt;&lt;span class=&quot;na&quot;&gt;key&lt;/span&gt; &lt;span class=&quot;o&quot;&gt;==&lt;/span&gt; &lt;span class=&quot;kc&quot;&gt;null&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;)&lt;/span&gt; &lt;span class=&quot;o&quot;&gt;{&lt;/span&gt;
            &lt;span class=&quot;n&quot;&gt;V&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;oldValue&lt;/span&gt; &lt;span class=&quot;o&quot;&gt;=&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;e&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;.&lt;/span&gt;&lt;span class=&quot;na&quot;&gt;value&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;;&lt;/span&gt;
            &lt;span class=&quot;n&quot;&gt;e&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;.&lt;/span&gt;&lt;span class=&quot;na&quot;&gt;value&lt;/span&gt; &lt;span class=&quot;o&quot;&gt;=&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;value&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;;&lt;/span&gt;
            &lt;span class=&quot;n&quot;&gt;e&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;.&lt;/span&gt;&lt;span class=&quot;na&quot;&gt;recordAccess&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;(&lt;/span&gt;&lt;span class=&quot;k&quot;&gt;this&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;);&lt;/span&gt;
            &lt;span class=&quot;k&quot;&gt;return&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;oldValue&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;;&lt;/span&gt;
        &lt;span class=&quot;o&quot;&gt;}&lt;/span&gt;
    &lt;span class=&quot;o&quot;&gt;}&lt;/span&gt;
    &lt;span class=&quot;n&quot;&gt;modCount&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;++;&lt;/span&gt;
    &lt;span class=&quot;n&quot;&gt;addEntry&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;(&lt;/span&gt;&lt;span class=&quot;mi&quot;&gt;0&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;,&lt;/span&gt; &lt;span class=&quot;kc&quot;&gt;null&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;,&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;value&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;,&lt;/span&gt; &lt;span class=&quot;mi&quot;&gt;0&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;);&lt;/span&gt;
    &lt;span class=&quot;k&quot;&gt;return&lt;/span&gt; &lt;span class=&quot;kc&quot;&gt;null&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;;&lt;/span&gt;
&lt;span class=&quot;o&quot;&gt;}&lt;/span&gt;
&lt;span class=&quot;cm&quot;&gt;/**
 * Adds a new entry with the specified key, value and hash code to
 * the specified bucket.  It is the responsibility of this
 * method to resize the table if appropriate.
 *
 * Subclass overrides this to alter the behavior of put method.
 */&lt;/span&gt;
&lt;span class=&quot;kt&quot;&gt;void&lt;/span&gt; &lt;span class=&quot;nf&quot;&gt;addEntry&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;(&lt;/span&gt;&lt;span class=&quot;kt&quot;&gt;int&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;hash&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;,&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;K&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;key&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;,&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;V&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;value&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;,&lt;/span&gt; &lt;span class=&quot;kt&quot;&gt;int&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;bucketIndex&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;)&lt;/span&gt; &lt;span class=&quot;o&quot;&gt;{&lt;/span&gt;
    &lt;span class=&quot;k&quot;&gt;if&lt;/span&gt; &lt;span class=&quot;o&quot;&gt;((&lt;/span&gt;&lt;span class=&quot;n&quot;&gt;size&lt;/span&gt; &lt;span class=&quot;o&quot;&gt;&amp;gt;=&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;threshold&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;)&lt;/span&gt; &lt;span class=&quot;o&quot;&gt;&amp;amp;&amp;amp;&lt;/span&gt; &lt;span class=&quot;o&quot;&gt;(&lt;/span&gt;&lt;span class=&quot;kc&quot;&gt;null&lt;/span&gt; &lt;span class=&quot;o&quot;&gt;!=&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;table&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;[&lt;/span&gt;&lt;span class=&quot;n&quot;&gt;bucketIndex&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;]))&lt;/span&gt; &lt;span class=&quot;o&quot;&gt;{&lt;/span&gt;
        &lt;span class=&quot;n&quot;&gt;resize&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;(&lt;/span&gt;&lt;span class=&quot;mi&quot;&gt;2&lt;/span&gt; &lt;span class=&quot;o&quot;&gt;*&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;table&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;.&lt;/span&gt;&lt;span class=&quot;na&quot;&gt;length&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;);&lt;/span&gt;
        &lt;span class=&quot;n&quot;&gt;hash&lt;/span&gt; &lt;span class=&quot;o&quot;&gt;=&lt;/span&gt; &lt;span class=&quot;o&quot;&gt;(&lt;/span&gt;&lt;span class=&quot;kc&quot;&gt;null&lt;/span&gt; &lt;span class=&quot;o&quot;&gt;!=&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;key&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;)&lt;/span&gt; &lt;span class=&quot;o&quot;&gt;?&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;hash&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;(&lt;/span&gt;&lt;span class=&quot;n&quot;&gt;key&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;)&lt;/span&gt; &lt;span class=&quot;o&quot;&gt;:&lt;/span&gt; &lt;span class=&quot;mi&quot;&gt;0&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;;&lt;/span&gt;
        &lt;span class=&quot;n&quot;&gt;bucketIndex&lt;/span&gt; &lt;span class=&quot;o&quot;&gt;=&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;indexFor&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;(&lt;/span&gt;&lt;span class=&quot;n&quot;&gt;hash&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;,&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;table&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;.&lt;/span&gt;&lt;span class=&quot;na&quot;&gt;length&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;);&lt;/span&gt;
    &lt;span class=&quot;o&quot;&gt;}&lt;/span&gt;

    &lt;span class=&quot;n&quot;&gt;createEntry&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;(&lt;/span&gt;&lt;span class=&quot;n&quot;&gt;hash&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;,&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;key&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;,&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;value&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;,&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;bucketIndex&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;);&lt;/span&gt;
&lt;span class=&quot;o&quot;&gt;}&lt;/span&gt;
&lt;span class=&quot;cm&quot;&gt;/**
 * Retrieve object hash code and applies a supplemental hash function to the
 * result hash, which defends against poor quality hash functions.  This is
 * critical because HashMap uses power-of-two length hash tables, that
 * otherwise encounter collisions for hashCodes that do not differ
 * in lower bits. Note: Null keys always map to hash 0, thus index 0.
 */&lt;/span&gt;
&lt;span class=&quot;kd&quot;&gt;final&lt;/span&gt; &lt;span class=&quot;kt&quot;&gt;int&lt;/span&gt; &lt;span class=&quot;nf&quot;&gt;hash&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;(&lt;/span&gt;&lt;span class=&quot;n&quot;&gt;Object&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;k&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;)&lt;/span&gt; &lt;span class=&quot;o&quot;&gt;{&lt;/span&gt;
    &lt;span class=&quot;kt&quot;&gt;int&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;h&lt;/span&gt; &lt;span class=&quot;o&quot;&gt;=&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;hashSeed&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;;&lt;/span&gt;
    &lt;span class=&quot;k&quot;&gt;if&lt;/span&gt; &lt;span class=&quot;o&quot;&gt;(&lt;/span&gt;&lt;span class=&quot;mi&quot;&gt;0&lt;/span&gt; &lt;span class=&quot;o&quot;&gt;!=&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;h&lt;/span&gt; &lt;span class=&quot;o&quot;&gt;&amp;amp;&amp;amp;&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;k&lt;/span&gt; &lt;span class=&quot;k&quot;&gt;instanceof&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;String&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;)&lt;/span&gt; &lt;span class=&quot;o&quot;&gt;{&lt;/span&gt;
        &lt;span class=&quot;k&quot;&gt;return&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;sun&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;.&lt;/span&gt;&lt;span class=&quot;na&quot;&gt;misc&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;.&lt;/span&gt;&lt;span class=&quot;na&quot;&gt;Hashing&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;.&lt;/span&gt;&lt;span class=&quot;na&quot;&gt;stringHash32&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;((&lt;/span&gt;&lt;span class=&quot;n&quot;&gt;String&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;)&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;k&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;);&lt;/span&gt;
    &lt;span class=&quot;o&quot;&gt;}&lt;/span&gt;

    &lt;span class=&quot;n&quot;&gt;h&lt;/span&gt; &lt;span class=&quot;o&quot;&gt;^=&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;k&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;.&lt;/span&gt;&lt;span class=&quot;na&quot;&gt;hashCode&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;();&lt;/span&gt;

    &lt;span class=&quot;c1&quot;&gt;// This function ensures that hashCodes that differ only by&lt;/span&gt;
    &lt;span class=&quot;c1&quot;&gt;// constant multiples at each bit position have a bounded&lt;/span&gt;
    &lt;span class=&quot;c1&quot;&gt;// number of collisions (approximately 8 at default load factor).&lt;/span&gt;
    &lt;span class=&quot;n&quot;&gt;h&lt;/span&gt; &lt;span class=&quot;o&quot;&gt;^=&lt;/span&gt; &lt;span class=&quot;o&quot;&gt;(&lt;/span&gt;&lt;span class=&quot;n&quot;&gt;h&lt;/span&gt; &lt;span class=&quot;o&quot;&gt;&amp;gt;&amp;gt;&amp;gt;&lt;/span&gt; &lt;span class=&quot;mi&quot;&gt;20&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;)&lt;/span&gt; &lt;span class=&quot;o&quot;&gt;^&lt;/span&gt; &lt;span class=&quot;o&quot;&gt;(&lt;/span&gt;&lt;span class=&quot;n&quot;&gt;h&lt;/span&gt; &lt;span class=&quot;o&quot;&gt;&amp;gt;&amp;gt;&amp;gt;&lt;/span&gt; &lt;span class=&quot;mi&quot;&gt;12&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;);&lt;/span&gt;
    &lt;span class=&quot;k&quot;&gt;return&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;h&lt;/span&gt; &lt;span class=&quot;o&quot;&gt;^&lt;/span&gt; &lt;span class=&quot;o&quot;&gt;(&lt;/span&gt;&lt;span class=&quot;n&quot;&gt;h&lt;/span&gt; &lt;span class=&quot;o&quot;&gt;&amp;gt;&amp;gt;&amp;gt;&lt;/span&gt; &lt;span class=&quot;mi&quot;&gt;7&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;)&lt;/span&gt; &lt;span class=&quot;o&quot;&gt;^&lt;/span&gt; &lt;span class=&quot;o&quot;&gt;(&lt;/span&gt;&lt;span class=&quot;n&quot;&gt;h&lt;/span&gt; &lt;span class=&quot;o&quot;&gt;&amp;gt;&amp;gt;&amp;gt;&lt;/span&gt; &lt;span class=&quot;mi&quot;&gt;4&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;);&lt;/span&gt;
&lt;span class=&quot;o&quot;&gt;}&lt;/span&gt;
&lt;span class=&quot;cm&quot;&gt;/**
 * Like addEntry except that this version is used when creating entries
 * as part of Map construction or &quot;pseudo-construction&quot; (cloning,
 * deserialization).  This version needn't worry about resizing the table.
 *
 * Subclass overrides this to alter the behavior of HashMap(Map),
 * clone, and readObject.
 */&lt;/span&gt;
&lt;span class=&quot;kt&quot;&gt;void&lt;/span&gt; &lt;span class=&quot;nf&quot;&gt;createEntry&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;(&lt;/span&gt;&lt;span class=&quot;kt&quot;&gt;int&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;hash&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;,&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;K&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;key&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;,&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;V&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;value&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;,&lt;/span&gt; &lt;span class=&quot;kt&quot;&gt;int&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;bucketIndex&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;)&lt;/span&gt; &lt;span class=&quot;o&quot;&gt;{&lt;/span&gt;
    &lt;span class=&quot;n&quot;&gt;Entry&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;&amp;lt;&lt;/span&gt;&lt;span class=&quot;n&quot;&gt;K&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;,&lt;/span&gt;&lt;span class=&quot;n&quot;&gt;V&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;&amp;gt;&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;e&lt;/span&gt; &lt;span class=&quot;o&quot;&gt;=&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;table&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;[&lt;/span&gt;&lt;span class=&quot;n&quot;&gt;bucketIndex&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;];&lt;/span&gt;
    &lt;span class=&quot;n&quot;&gt;table&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;[&lt;/span&gt;&lt;span class=&quot;n&quot;&gt;bucketIndex&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;]&lt;/span&gt; &lt;span class=&quot;o&quot;&gt;=&lt;/span&gt; &lt;span class=&quot;k&quot;&gt;new&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;Entry&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;&amp;lt;&amp;gt;(&lt;/span&gt;&lt;span class=&quot;n&quot;&gt;hash&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;,&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;key&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;,&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;value&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;,&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;e&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;);&lt;/span&gt;
    &lt;span class=&quot;n&quot;&gt;size&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;++;&lt;/span&gt;
&lt;span class=&quot;o&quot;&gt;}&lt;/span&gt;
&lt;/code&gt;&lt;/pre&gt;
        &lt;/div&gt;
      &lt;/li&gt;
    &lt;/ul&gt;
  &lt;/li&gt;
  &lt;li&gt;jdk 1.8&lt;/li&gt;
&lt;/ul&gt;

&lt;div class=&quot;language-java highlighter-rouge&quot;&gt;&lt;pre class=&quot;highlight&quot;&gt;&lt;code&gt;&lt;span class=&quot;kd&quot;&gt;final&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;V&lt;/span&gt; &lt;span class=&quot;nf&quot;&gt;putVal&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;(&lt;/span&gt;&lt;span class=&quot;kt&quot;&gt;int&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;hash&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;,&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;K&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;key&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;,&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;V&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;value&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;,&lt;/span&gt; &lt;span class=&quot;kt&quot;&gt;boolean&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;onlyIfAbsent&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;,&lt;/span&gt; &lt;span class=&quot;kt&quot;&gt;boolean&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;evict&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;)&lt;/span&gt; &lt;span class=&quot;o&quot;&gt;{&lt;/span&gt;
  &lt;span class=&quot;n&quot;&gt;Node&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;&amp;lt;&lt;/span&gt;&lt;span class=&quot;n&quot;&gt;K&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;,&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;V&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;&amp;gt;[]&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;tab&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;;&lt;/span&gt;
  &lt;span class=&quot;n&quot;&gt;Node&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;&amp;lt;&lt;/span&gt;&lt;span class=&quot;n&quot;&gt;K&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;,&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;V&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;&amp;gt;&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;p&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;;&lt;/span&gt;
  &lt;span class=&quot;kt&quot;&gt;int&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;n&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;,&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;i&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;;&lt;/span&gt;
  &lt;span class=&quot;c1&quot;&gt;// 若table为空或table的length为0则需要通过resize方法扩容&lt;/span&gt;
  &lt;span class=&quot;k&quot;&gt;if&lt;/span&gt; &lt;span class=&quot;o&quot;&gt;((&lt;/span&gt;&lt;span class=&quot;n&quot;&gt;tab&lt;/span&gt; &lt;span class=&quot;o&quot;&gt;=&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;table&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;)&lt;/span&gt; &lt;span class=&quot;o&quot;&gt;==&lt;/span&gt; &lt;span class=&quot;kc&quot;&gt;null&lt;/span&gt; &lt;span class=&quot;o&quot;&gt;||&lt;/span&gt; &lt;span class=&quot;o&quot;&gt;(&lt;/span&gt;&lt;span class=&quot;n&quot;&gt;n&lt;/span&gt; &lt;span class=&quot;o&quot;&gt;=&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;tab&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;.&lt;/span&gt;&lt;span class=&quot;na&quot;&gt;length&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;)&lt;/span&gt; &lt;span class=&quot;o&quot;&gt;==&lt;/span&gt; &lt;span class=&quot;mi&quot;&gt;0&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;)&lt;/span&gt;
    &lt;span class=&quot;n&quot;&gt;n&lt;/span&gt; &lt;span class=&quot;o&quot;&gt;=&lt;/span&gt; &lt;span class=&quot;o&quot;&gt;(&lt;/span&gt;&lt;span class=&quot;n&quot;&gt;tab&lt;/span&gt; &lt;span class=&quot;o&quot;&gt;=&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;resize&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;()).&lt;/span&gt;&lt;span class=&quot;na&quot;&gt;length&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;;&lt;/span&gt;
  &lt;span class=&quot;c1&quot;&gt;// 让传入的hash与n-1做与运算从而得到目标Node的索引&lt;/span&gt;
  &lt;span class=&quot;c1&quot;&gt;// 若该索引处为null，则直接插入包含了key-value pair的new Node&lt;/span&gt;
  &lt;span class=&quot;k&quot;&gt;if&lt;/span&gt; &lt;span class=&quot;o&quot;&gt;((&lt;/span&gt;&lt;span class=&quot;n&quot;&gt;p&lt;/span&gt; &lt;span class=&quot;o&quot;&gt;=&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;tab&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;[&lt;/span&gt;&lt;span class=&quot;n&quot;&gt;i&lt;/span&gt; &lt;span class=&quot;o&quot;&gt;=&lt;/span&gt; &lt;span class=&quot;o&quot;&gt;(&lt;/span&gt;&lt;span class=&quot;n&quot;&gt;n&lt;/span&gt; &lt;span class=&quot;o&quot;&gt;-&lt;/span&gt; &lt;span class=&quot;mi&quot;&gt;1&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;)&lt;/span&gt; &lt;span class=&quot;o&quot;&gt;&amp;amp;&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;hash&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;])&lt;/span&gt; &lt;span class=&quot;o&quot;&gt;==&lt;/span&gt; &lt;span class=&quot;kc&quot;&gt;null&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;)&lt;/span&gt;
    &lt;span class=&quot;n&quot;&gt;tab&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;[&lt;/span&gt;&lt;span class=&quot;n&quot;&gt;i&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;]&lt;/span&gt; &lt;span class=&quot;o&quot;&gt;=&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;newNode&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;(&lt;/span&gt;&lt;span class=&quot;n&quot;&gt;hash&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;,&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;key&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;,&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;value&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;,&lt;/span&gt; &lt;span class=&quot;kc&quot;&gt;null&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;);&lt;/span&gt;
  &lt;span class=&quot;k&quot;&gt;else&lt;/span&gt; &lt;span class=&quot;o&quot;&gt;{&lt;/span&gt;
    &lt;span class=&quot;c1&quot;&gt;// 若索引处不为null，则判断key是否存在&lt;/span&gt;
    &lt;span class=&quot;n&quot;&gt;Node&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;&amp;lt;&lt;/span&gt;&lt;span class=&quot;n&quot;&gt;K&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;,&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;V&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;&amp;gt;&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;e&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;;&lt;/span&gt;
    &lt;span class=&quot;n&quot;&gt;K&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;k&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;;&lt;/span&gt;
    &lt;span class=&quot;c1&quot;&gt;// 若key存在，则直接覆盖value&lt;/span&gt;
    &lt;span class=&quot;k&quot;&gt;if&lt;/span&gt; &lt;span class=&quot;o&quot;&gt;(&lt;/span&gt;&lt;span class=&quot;n&quot;&gt;p&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;.&lt;/span&gt;&lt;span class=&quot;na&quot;&gt;hash&lt;/span&gt; &lt;span class=&quot;o&quot;&gt;==&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;hash&lt;/span&gt;
        &lt;span class=&quot;o&quot;&gt;&amp;amp;&amp;amp;&lt;/span&gt; &lt;span class=&quot;o&quot;&gt;((&lt;/span&gt;&lt;span class=&quot;n&quot;&gt;k&lt;/span&gt; &lt;span class=&quot;o&quot;&gt;=&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;p&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;.&lt;/span&gt;&lt;span class=&quot;na&quot;&gt;key&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;)&lt;/span&gt; &lt;span class=&quot;o&quot;&gt;==&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;key&lt;/span&gt; &lt;span class=&quot;o&quot;&gt;||&lt;/span&gt; &lt;span class=&quot;o&quot;&gt;(&lt;/span&gt;&lt;span class=&quot;n&quot;&gt;key&lt;/span&gt; &lt;span class=&quot;o&quot;&gt;!=&lt;/span&gt; &lt;span class=&quot;kc&quot;&gt;null&lt;/span&gt; &lt;span class=&quot;o&quot;&gt;&amp;amp;&amp;amp;&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;key&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;.&lt;/span&gt;&lt;span class=&quot;na&quot;&gt;equals&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;(&lt;/span&gt;&lt;span class=&quot;n&quot;&gt;k&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;))))&lt;/span&gt;
      &lt;span class=&quot;n&quot;&gt;e&lt;/span&gt; &lt;span class=&quot;o&quot;&gt;=&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;p&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;;&lt;/span&gt;
    &lt;span class=&quot;c1&quot;&gt;// 若key不存在，则判断table[i]是否为TreeNode&lt;/span&gt;
    &lt;span class=&quot;k&quot;&gt;else&lt;/span&gt; &lt;span class=&quot;nf&quot;&gt;if&lt;/span&gt; &lt;span class=&quot;o&quot;&gt;(&lt;/span&gt;&lt;span class=&quot;n&quot;&gt;p&lt;/span&gt; &lt;span class=&quot;k&quot;&gt;instanceof&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;TreeNode&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;)&lt;/span&gt;
      &lt;span class=&quot;c1&quot;&gt;// 若是的话，说明此处为红黑树，直接插入key-value pair&lt;/span&gt;
      &lt;span class=&quot;n&quot;&gt;e&lt;/span&gt; &lt;span class=&quot;o&quot;&gt;=&lt;/span&gt; &lt;span class=&quot;o&quot;&gt;((&lt;/span&gt;&lt;span class=&quot;n&quot;&gt;TreeNode&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;&amp;lt;&lt;/span&gt;&lt;span class=&quot;n&quot;&gt;K&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;,&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;V&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;&amp;gt;)&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;p&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;).&lt;/span&gt;&lt;span class=&quot;na&quot;&gt;putTreeVal&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;(&lt;/span&gt;&lt;span class=&quot;k&quot;&gt;this&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;,&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;tab&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;,&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;hash&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;,&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;key&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;,&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;value&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;);&lt;/span&gt;
      &lt;span class=&quot;c1&quot;&gt;// 否则遍历链表&lt;/span&gt;
    &lt;span class=&quot;k&quot;&gt;else&lt;/span&gt; &lt;span class=&quot;o&quot;&gt;{&lt;/span&gt;
      &lt;span class=&quot;k&quot;&gt;for&lt;/span&gt; &lt;span class=&quot;o&quot;&gt;(&lt;/span&gt;&lt;span class=&quot;kt&quot;&gt;int&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;binCount&lt;/span&gt; &lt;span class=&quot;o&quot;&gt;=&lt;/span&gt; &lt;span class=&quot;mi&quot;&gt;0&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;;;&lt;/span&gt; &lt;span class=&quot;o&quot;&gt;++&lt;/span&gt;&lt;span class=&quot;n&quot;&gt;binCount&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;)&lt;/span&gt; &lt;span class=&quot;o&quot;&gt;{&lt;/span&gt;
        &lt;span class=&quot;k&quot;&gt;if&lt;/span&gt; &lt;span class=&quot;o&quot;&gt;((&lt;/span&gt;&lt;span class=&quot;n&quot;&gt;e&lt;/span&gt; &lt;span class=&quot;o&quot;&gt;=&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;p&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;.&lt;/span&gt;&lt;span class=&quot;na&quot;&gt;next&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;)&lt;/span&gt; &lt;span class=&quot;o&quot;&gt;==&lt;/span&gt; &lt;span class=&quot;kc&quot;&gt;null&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;)&lt;/span&gt; &lt;span class=&quot;o&quot;&gt;{&lt;/span&gt;
          &lt;span class=&quot;n&quot;&gt;p&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;.&lt;/span&gt;&lt;span class=&quot;na&quot;&gt;next&lt;/span&gt; &lt;span class=&quot;o&quot;&gt;=&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;newNode&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;(&lt;/span&gt;&lt;span class=&quot;n&quot;&gt;hash&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;,&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;key&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;,&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;value&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;,&lt;/span&gt; &lt;span class=&quot;kc&quot;&gt;null&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;);&lt;/span&gt;
          &lt;span class=&quot;c1&quot;&gt;// 链表长度大于8则转为红黑树&lt;/span&gt;
          &lt;span class=&quot;k&quot;&gt;if&lt;/span&gt; &lt;span class=&quot;o&quot;&gt;(&lt;/span&gt;&lt;span class=&quot;n&quot;&gt;binCount&lt;/span&gt; &lt;span class=&quot;o&quot;&gt;&amp;gt;=&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;TREEIFY_THRESHOLD&lt;/span&gt; &lt;span class=&quot;o&quot;&gt;-&lt;/span&gt; &lt;span class=&quot;mi&quot;&gt;1&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;)&lt;/span&gt; &lt;span class=&quot;c1&quot;&gt;// -1 for 1st&lt;/span&gt;
            &lt;span class=&quot;n&quot;&gt;treeifyBin&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;(&lt;/span&gt;&lt;span class=&quot;n&quot;&gt;tab&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;,&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;hash&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;);&lt;/span&gt;
          &lt;span class=&quot;k&quot;&gt;break&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;;&lt;/span&gt;
        &lt;span class=&quot;o&quot;&gt;}&lt;/span&gt;
        &lt;span class=&quot;c1&quot;&gt;// 若key已经存在则直接覆盖value&lt;/span&gt;
        &lt;span class=&quot;k&quot;&gt;if&lt;/span&gt; &lt;span class=&quot;o&quot;&gt;(&lt;/span&gt;&lt;span class=&quot;n&quot;&gt;e&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;.&lt;/span&gt;&lt;span class=&quot;na&quot;&gt;hash&lt;/span&gt; &lt;span class=&quot;o&quot;&gt;==&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;hash&lt;/span&gt;
            &lt;span class=&quot;o&quot;&gt;&amp;amp;&amp;amp;&lt;/span&gt; &lt;span class=&quot;o&quot;&gt;((&lt;/span&gt;&lt;span class=&quot;n&quot;&gt;k&lt;/span&gt; &lt;span class=&quot;o&quot;&gt;=&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;e&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;.&lt;/span&gt;&lt;span class=&quot;na&quot;&gt;key&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;)&lt;/span&gt; &lt;span class=&quot;o&quot;&gt;==&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;key&lt;/span&gt; &lt;span class=&quot;o&quot;&gt;||&lt;/span&gt; &lt;span class=&quot;o&quot;&gt;(&lt;/span&gt;&lt;span class=&quot;n&quot;&gt;key&lt;/span&gt; &lt;span class=&quot;o&quot;&gt;!=&lt;/span&gt; &lt;span class=&quot;kc&quot;&gt;null&lt;/span&gt; &lt;span class=&quot;o&quot;&gt;&amp;amp;&amp;amp;&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;key&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;.&lt;/span&gt;&lt;span class=&quot;na&quot;&gt;equals&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;(&lt;/span&gt;&lt;span class=&quot;n&quot;&gt;k&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;))))&lt;/span&gt;
          &lt;span class=&quot;k&quot;&gt;break&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;;&lt;/span&gt;
        &lt;span class=&quot;n&quot;&gt;p&lt;/span&gt; &lt;span class=&quot;o&quot;&gt;=&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;e&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;;&lt;/span&gt;
      &lt;span class=&quot;o&quot;&gt;}&lt;/span&gt;
    &lt;span class=&quot;o&quot;&gt;}&lt;/span&gt;
    &lt;span class=&quot;k&quot;&gt;if&lt;/span&gt; &lt;span class=&quot;o&quot;&gt;(&lt;/span&gt;&lt;span class=&quot;n&quot;&gt;e&lt;/span&gt; &lt;span class=&quot;o&quot;&gt;!=&lt;/span&gt; &lt;span class=&quot;kc&quot;&gt;null&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;)&lt;/span&gt; &lt;span class=&quot;o&quot;&gt;{&lt;/span&gt; &lt;span class=&quot;c1&quot;&gt;// existing mapping for key&lt;/span&gt;
      &lt;span class=&quot;n&quot;&gt;V&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;oldValue&lt;/span&gt; &lt;span class=&quot;o&quot;&gt;=&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;e&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;.&lt;/span&gt;&lt;span class=&quot;na&quot;&gt;value&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;;&lt;/span&gt;
      &lt;span class=&quot;k&quot;&gt;if&lt;/span&gt; &lt;span class=&quot;o&quot;&gt;(!&lt;/span&gt;&lt;span class=&quot;n&quot;&gt;onlyIfAbsent&lt;/span&gt; &lt;span class=&quot;o&quot;&gt;||&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;oldValue&lt;/span&gt; &lt;span class=&quot;o&quot;&gt;==&lt;/span&gt; &lt;span class=&quot;kc&quot;&gt;null&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;)&lt;/span&gt;
        &lt;span class=&quot;n&quot;&gt;e&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;.&lt;/span&gt;&lt;span class=&quot;na&quot;&gt;value&lt;/span&gt; &lt;span class=&quot;o&quot;&gt;=&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;value&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;;&lt;/span&gt;
      &lt;span class=&quot;n&quot;&gt;afterNodeAccess&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;(&lt;/span&gt;&lt;span class=&quot;n&quot;&gt;e&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;);&lt;/span&gt;
      &lt;span class=&quot;k&quot;&gt;return&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;oldValue&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;;&lt;/span&gt;
    &lt;span class=&quot;o&quot;&gt;}&lt;/span&gt;
  &lt;span class=&quot;o&quot;&gt;}&lt;/span&gt;
  &lt;span class=&quot;o&quot;&gt;++&lt;/span&gt;&lt;span class=&quot;n&quot;&gt;modCount&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;;&lt;/span&gt;
  &lt;span class=&quot;c1&quot;&gt;// 若超过maxSize，则扩容&lt;/span&gt;
  &lt;span class=&quot;k&quot;&gt;if&lt;/span&gt; &lt;span class=&quot;o&quot;&gt;(++&lt;/span&gt;&lt;span class=&quot;n&quot;&gt;size&lt;/span&gt; &lt;span class=&quot;o&quot;&gt;&amp;gt;&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;threshold&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;)&lt;/span&gt;
    &lt;span class=&quot;n&quot;&gt;resize&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;();&lt;/span&gt;
  &lt;span class=&quot;n&quot;&gt;afterNodeInsertion&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;(&lt;/span&gt;&lt;span class=&quot;n&quot;&gt;evict&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;);&lt;/span&gt;
  &lt;span class=&quot;k&quot;&gt;return&lt;/span&gt; &lt;span class=&quot;kc&quot;&gt;null&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;;&lt;/span&gt;
&lt;span class=&quot;o&quot;&gt;}&lt;/span&gt;
&lt;/code&gt;&lt;/pre&gt;
&lt;/div&gt;

&lt;p&gt;以上代码的工作过程可以总结为下图：&lt;/p&gt;
&lt;figure&gt;
  &lt;img src=&quot;http://upload-images.jianshu.io/upload_images/2397836-6450610b8603539c.png?imageMogr2/auto-orient/strip%7CimageView2/2/w/1240&quot; /&gt;
&lt;/figure&gt;

&lt;blockquote&gt;
  &lt;p&gt;&lt;a href=&quot;http://www.jianshu.com/p/f174d49b391c?hmsr=toutiao.io&amp;amp;utm_medium=toutiao.io&amp;amp;utm_source=toutiao.io&quot;&gt;从源码角度认识ArrayList，LinkedList与HashMap&lt;/a&gt;
&lt;a href=&quot;https://zhuanlan.zhihu.com/p/21673805&quot;&gt;Java 8系列之重新认识HashMap&lt;/a&gt;&lt;/p&gt;
&lt;/blockquote&gt;

&lt;h1 id=&quot;section&quot;&gt;拓展&lt;/h1&gt;
&lt;h1 id=&quot;hashmaphttpwwwimportnewcom7099html&quot;&gt;&lt;a href=&quot;http://www.importnew.com/7099.html&quot;&gt;HashMap的工作原理&lt;/a&gt;&lt;/h1&gt;

&lt;h2 id=&quot;qhashmap-hashmap&quot;&gt;Q：“你用过HashMap吗？” “什么是HashMap？你为什么用到它？”&lt;/h2&gt;

&lt;h2 id=&quot;qhashmap-hashmapget&quot;&gt;Q：“你知道HashMap的工作原理吗？” “你知道HashMap的get()方法的工作原理吗？”&lt;/h2&gt;

&lt;h2 id=&quot;qhashmapcollision-detectionhashcode&quot;&gt;Q：关于HashMap中的碰撞探测(collision detection)以及碰撞的解决方法？“当两个对象的hashcode相同会发生什么？”&lt;/h2&gt;

&lt;h2 id=&quot;qhashcode&quot;&gt;Q：“如果两个键的hashcode相同，你如何获取值对象？”&lt;/h2&gt;

&lt;h2 id=&quot;qhashmapload-factorhashmap075map75bucketarraylisthashmapbucketmapbucketrehashinghashbucket&quot;&gt;Q：“如果HashMap的大小超过了负载因子(load factor)定义的容量，怎么办？”除非你真正知道HashMap的工作原理，否则你将回答不出这道题。默认的负载因子大小为0.75，也就是说，当一个map填满了75%的bucket时候，和其它集合类(如ArrayList等)一样，将会创建原来HashMap大小的两倍的bucket数组，来重新调整map的大小，并将原来的对象放入新的bucket数组中。这个过程叫作rehashing，因为它调用hash方法找到新的bucket位置。&lt;/h2&gt;

&lt;h2 id=&quot;qhashmap&quot;&gt;Q：“你了解重新调整HashMap大小存在什么问题吗？”&lt;/h2&gt;

&lt;h2 id=&quot;qstring-intergerwrapper-&quot;&gt;Q：为什么String, Interger这样的wrapper类适合作为键？ 我们可以使用自定义的对象作为键吗？&lt;/h2&gt;

&lt;h2 id=&quot;qcocurrenthashmaphashtable&quot;&gt;Q：我们可以使用CocurrentHashMap来代替Hashtable吗？&lt;/h2&gt;

&lt;p&gt;查看&lt;a href=&quot;http://javarevisited.blogspot.com/2011/04/difference-between-concurrenthashmap.html/&quot;&gt;Hashtable和ConcurrentHashMap的区别&lt;/a&gt;。&lt;/p&gt;

&lt;p&gt;我个人很喜欢这个问题，因为这个问题的深度和广度，也不直接的涉及到不同的概念。让我们再来看看这些问题设计哪些知识点：&lt;/p&gt;
&lt;ul&gt;
  &lt;li&gt;hashing的概念&lt;/li&gt;
  &lt;li&gt;HashMap中解决碰撞的方法&lt;/li&gt;
  &lt;li&gt;equals()和hashCode()的应用，以及它们在HashMap中的重要性&lt;/li&gt;
  &lt;li&gt;不可变对象的好处&lt;/li&gt;
  &lt;li&gt;HashMap多线程的条件竞争&lt;/li&gt;
  &lt;li&gt;重新调整HashMap的大小&lt;/li&gt;
&lt;/ul&gt;

&lt;p&gt;因为HashMap的好处非常多，我曾经在电子商务的应用中使用HashMap作为缓存。因为金融领域非常多的运用Java，也出于性能的考虑，我们会经常用到HashMap和ConcurrentHashMap。你可以查看更多的关于HashMap的文章:&lt;/p&gt;

&lt;p&gt;&lt;a href=&quot;http://www.importnew.com/7010.html/&quot;&gt;HashMap和Hashtable的区别&lt;/a&gt;
&lt;a href=&quot;http://www.importnew.com/6931.html/&quot;&gt;HashMap和HashSet的区别&lt;/a&gt;&lt;/p&gt;</content><category term="JavaBasic" /><summary type="html">HashMap源码分析.</summary></entry><entry><title type="html">Java源码分析——LinkedList</title><link href="https://ckape.github.io/workhard/LinkedList/" rel="alternate" type="text/html" title="Java源码分析——LinkedList" /><published>2016-09-20T00:00:00+08:00</published><updated>2016-09-20T00:00:00+08:00</updated><id>https://ckape.github.io/workhard/LinkedList</id><content type="html" xml:base="https://ckape.github.io/workhard/LinkedList/">&lt;h2 id=&quot;linkedlist&quot;&gt;LinkedList&lt;/h2&gt;
&lt;blockquote&gt;
  &lt;p&gt;参考学习资料：&lt;/p&gt;
  &lt;blockquote&gt;
    &lt;p&gt;JDK1.7之前的【Java集合源码剖析】LinkedList源码剖析&lt;/p&gt;
  &lt;/blockquote&gt;
&lt;/blockquote&gt;

&lt;ol&gt;
  &lt;li&gt;LinkedList的要点
    &lt;ul&gt;
      &lt;li&gt;&lt;strong&gt;双向链表&lt;/strong&gt;：LinkedList基于双向链表实现的（Entry有next，previous指针），因此可以把它当栈，队列和双端队列使用；
在JDK1.7之前LinkedList之前是循环链表的方式实现两端插入的，包含一个无值的头结点，JDK1.7及以上是包含两个指针分别指向头结点和尾结点；&lt;/li&gt;
      &lt;li&gt;&lt;strong&gt;线程不安全&lt;/strong&gt;：LinkedList通过维护modCount修改计数，每个迭代器保存各自的修改计数与modCount对比检验的方式防止并发修改；&lt;/li&gt;
      &lt;li&gt;&lt;strong&gt;性能特点&lt;/strong&gt;：由于是链表实现，不支持快速随机存取，因此get(index)效率不高，在循环时一定注意不能误用；支持高效的结构性修改（只需要移动指针指向）；因此LinkedList定义了内部类实现ListIterator，避免使用效率低下的get()（AbstractList的迭代器是基于get()的），iterator()返回也是这个内部类实例；&lt;/li&gt;
      &lt;li&gt;&lt;strong&gt;克隆和序列化&lt;/strong&gt;：实现了Serializable和Cloneable接口，支持序列化和克隆，其中序列化使用writeObject和readObject不采用默认的序列化机制，只保存size和元素对象，一方面是隐藏内部表示信息，一方面节省了开销；&lt;/li&gt;
      &lt;li&gt;&lt;strong&gt;置空操作&lt;/strong&gt;：强调一点，对应容器，删除结点时x = null;是很有必要的，让容器，容器中的结点在清除后不要互相引用的保存在堆中，影响垃圾回收，因为JVM一般是进行可达性分析的；&lt;/li&gt;
    &lt;/ul&gt;
  &lt;/li&gt;
  &lt;li&gt;基本结构
    &lt;ul&gt;
      &lt;li&gt;结点类
        &lt;ul&gt;
          &lt;li&gt;双向链表，链表包含2个指针：头结点指针，尾结点指针；&lt;/li&gt;
          &lt;li&gt;结点（Node），包含2个指针，指向前驱结点和后序结点；&lt;/li&gt;
        &lt;/ul&gt;
      &lt;/li&gt;
    &lt;/ul&gt;
  &lt;/li&gt;
&lt;/ol&gt;

&lt;figure class=&quot;highlight&quot;&gt;&lt;pre&gt;&lt;code class=&quot;language-java&quot; data-lang=&quot;java&quot;&gt;      &lt;span class=&quot;kd&quot;&gt;transient&lt;/span&gt; &lt;span class=&quot;kt&quot;&gt;int&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;size&lt;/span&gt; &lt;span class=&quot;o&quot;&gt;=&lt;/span&gt; &lt;span class=&quot;mi&quot;&gt;0&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;;&lt;/span&gt;    
      &lt;span class=&quot;c1&quot;&gt;//不变式：(first == null &amp;amp;&amp;amp; last == null) || (first.prev == null &amp;amp;&amp;amp; first.item != null)&lt;/span&gt;
      &lt;span class=&quot;kd&quot;&gt;transient&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;Node&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;&amp;lt;&lt;/span&gt;&lt;span class=&quot;n&quot;&gt;E&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;&amp;gt;&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;first&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;;&lt;/span&gt;
      &lt;span class=&quot;c1&quot;&gt;//不变式：(first == null &amp;amp;&amp;amp; last == null) || (last.next == null &amp;amp;&amp;amp; last.item != null)&lt;/span&gt;
      &lt;span class=&quot;kd&quot;&gt;transient&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;Node&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;&amp;lt;&lt;/span&gt;&lt;span class=&quot;n&quot;&gt;E&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;&amp;gt;&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;last&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;;&lt;/span&gt;
      &lt;span class=&quot;c1&quot;&gt;//结点&lt;/span&gt;
      &lt;span class=&quot;kd&quot;&gt;private&lt;/span&gt; &lt;span class=&quot;kd&quot;&gt;static&lt;/span&gt; &lt;span class=&quot;kd&quot;&gt;class&lt;/span&gt; &lt;span class=&quot;nc&quot;&gt;Node&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;&amp;lt;&lt;/span&gt;&lt;span class=&quot;n&quot;&gt;E&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;&amp;gt;&lt;/span&gt; &lt;span class=&quot;o&quot;&gt;{&lt;/span&gt;
          &lt;span class=&quot;n&quot;&gt;E&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;item&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;;&lt;/span&gt;
          &lt;span class=&quot;n&quot;&gt;Node&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;&amp;lt;&lt;/span&gt;&lt;span class=&quot;n&quot;&gt;E&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;&amp;gt;&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;next&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;;&lt;/span&gt;
          &lt;span class=&quot;n&quot;&gt;Node&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;&amp;lt;&lt;/span&gt;&lt;span class=&quot;n&quot;&gt;E&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;&amp;gt;&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;prev&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;;&lt;/span&gt;
          &lt;span class=&quot;n&quot;&gt;Node&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;(&lt;/span&gt;&lt;span class=&quot;n&quot;&gt;Node&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;&amp;lt;&lt;/span&gt;&lt;span class=&quot;n&quot;&gt;E&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;&amp;gt;&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;prev&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;,&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;E&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;element&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;,&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;Node&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;&amp;lt;&lt;/span&gt;&lt;span class=&quot;n&quot;&gt;E&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;&amp;gt;&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;next&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;)&lt;/span&gt; &lt;span class=&quot;o&quot;&gt;{&lt;/span&gt;
              &lt;span class=&quot;k&quot;&gt;this&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;.&lt;/span&gt;&lt;span class=&quot;na&quot;&gt;item&lt;/span&gt; &lt;span class=&quot;o&quot;&gt;=&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;element&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;;&lt;/span&gt;
              &lt;span class=&quot;k&quot;&gt;this&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;.&lt;/span&gt;&lt;span class=&quot;na&quot;&gt;next&lt;/span&gt; &lt;span class=&quot;o&quot;&gt;=&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;next&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;;&lt;/span&gt;
              &lt;span class=&quot;k&quot;&gt;this&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;.&lt;/span&gt;&lt;span class=&quot;na&quot;&gt;prev&lt;/span&gt; &lt;span class=&quot;o&quot;&gt;=&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;prev&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;;&lt;/span&gt;
          &lt;span class=&quot;o&quot;&gt;}&lt;/span&gt;
      &lt;span class=&quot;o&quot;&gt;}&lt;/span&gt;&lt;/code&gt;&lt;/pre&gt;&lt;/figure&gt;

&lt;ul&gt;
  &lt;li&gt;列表迭代器ListIterator非静态内部类实现
    &lt;ul&gt;
      &lt;li&gt;每个迭代器对象独立维护一个expectedModCount进行修改计数检查，每次进行修改操作之前（包括set方法）检查计数，防止并发修改（抛出ConcurrentModificationException异常）；&lt;/li&gt;
      &lt;li&gt;lastReturned这个变量很关键，结构性修改一次之后（add和remove）这个变量被置空，因此对于迭代器调用一次add或remove之后调用next才可以在此remove和set；&lt;/li&gt;
      &lt;li&gt;ListIterator支持两个方向的迭代遍历；
        &lt;div class=&quot;language-java highlighter-rouge&quot;&gt;&lt;pre class=&quot;highlight&quot;&gt;&lt;code&gt;  &lt;span class=&quot;kd&quot;&gt;private&lt;/span&gt; &lt;span class=&quot;kd&quot;&gt;class&lt;/span&gt; &lt;span class=&quot;nc&quot;&gt;ListItr&lt;/span&gt; &lt;span class=&quot;kd&quot;&gt;implements&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;ListIterator&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;&amp;lt;&lt;/span&gt;&lt;span class=&quot;n&quot;&gt;E&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;&amp;gt;&lt;/span&gt; &lt;span class=&quot;o&quot;&gt;{&lt;/span&gt;
      &lt;span class=&quot;c1&quot;&gt;//lastReturned保存最后返回的结点引用，当add，remove结构性修改后将这个值置空用于标识结构结构已修改&lt;/span&gt;
      &lt;span class=&quot;kd&quot;&gt;private&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;Node&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;&amp;lt;&lt;/span&gt;&lt;span class=&quot;n&quot;&gt;E&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;&amp;gt;&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;lastReturned&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;;&lt;/span&gt;
      &lt;span class=&quot;kd&quot;&gt;private&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;Node&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;&amp;lt;&lt;/span&gt;&lt;span class=&quot;n&quot;&gt;E&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;&amp;gt;&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;next&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;;&lt;/span&gt;
      &lt;span class=&quot;kd&quot;&gt;private&lt;/span&gt; &lt;span class=&quot;kt&quot;&gt;int&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;nextIndex&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;;&lt;/span&gt;
      &lt;span class=&quot;c1&quot;&gt;//每个迭代器保存创建时modCount，维护自己的modCount防止因为并发修改造成的不一致&lt;/span&gt;
      &lt;span class=&quot;kd&quot;&gt;private&lt;/span&gt; &lt;span class=&quot;kt&quot;&gt;int&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;expectedModCount&lt;/span&gt; &lt;span class=&quot;o&quot;&gt;=&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;modCount&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;;&lt;/span&gt;
      &lt;span class=&quot;n&quot;&gt;ListItr&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;(&lt;/span&gt;&lt;span class=&quot;kt&quot;&gt;int&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;index&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;)&lt;/span&gt; &lt;span class=&quot;o&quot;&gt;{&lt;/span&gt;
          &lt;span class=&quot;n&quot;&gt;next&lt;/span&gt; &lt;span class=&quot;o&quot;&gt;=&lt;/span&gt; &lt;span class=&quot;o&quot;&gt;(&lt;/span&gt;&lt;span class=&quot;n&quot;&gt;index&lt;/span&gt; &lt;span class=&quot;o&quot;&gt;==&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;size&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;)&lt;/span&gt; &lt;span class=&quot;o&quot;&gt;?&lt;/span&gt; &lt;span class=&quot;kc&quot;&gt;null&lt;/span&gt; &lt;span class=&quot;o&quot;&gt;:&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;node&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;(&lt;/span&gt;&lt;span class=&quot;n&quot;&gt;index&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;);&lt;/span&gt;
          &lt;span class=&quot;n&quot;&gt;nextIndex&lt;/span&gt; &lt;span class=&quot;o&quot;&gt;=&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;index&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;;&lt;/span&gt;
      &lt;span class=&quot;o&quot;&gt;}&lt;/span&gt;
      &lt;span class=&quot;nd&quot;&gt;@Override&lt;/span&gt;
      &lt;span class=&quot;kd&quot;&gt;public&lt;/span&gt; &lt;span class=&quot;kt&quot;&gt;void&lt;/span&gt; &lt;span class=&quot;nf&quot;&gt;add&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;(&lt;/span&gt;&lt;span class=&quot;n&quot;&gt;E&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;e&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;)&lt;/span&gt; &lt;span class=&quot;o&quot;&gt;{&lt;/span&gt;
          &lt;span class=&quot;c1&quot;&gt;//每次结构性修改之前必须先检查modCount是否同步，保证同时只有一个ListIterator可以修改链表&lt;/span&gt;
          &lt;span class=&quot;n&quot;&gt;checkForComodification&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;();&lt;/span&gt;
          &lt;span class=&quot;c1&quot;&gt;//lastReturned置空，防止删除之前的结点&lt;/span&gt;
          &lt;span class=&quot;n&quot;&gt;lastReturned&lt;/span&gt; &lt;span class=&quot;o&quot;&gt;=&lt;/span&gt; &lt;span class=&quot;kc&quot;&gt;null&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;;&lt;/span&gt;
          &lt;span class=&quot;k&quot;&gt;if&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;(&lt;/span&gt;&lt;span class=&quot;n&quot;&gt;next&lt;/span&gt; &lt;span class=&quot;o&quot;&gt;==&lt;/span&gt; &lt;span class=&quot;kc&quot;&gt;null&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;)&lt;/span&gt;
              &lt;span class=&quot;n&quot;&gt;linkLast&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;(&lt;/span&gt;&lt;span class=&quot;n&quot;&gt;e&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;);&lt;/span&gt;
          &lt;span class=&quot;k&quot;&gt;else&lt;/span&gt;
              &lt;span class=&quot;nf&quot;&gt;linkBefore&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;(&lt;/span&gt;&lt;span class=&quot;n&quot;&gt;e&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;,&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;next&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;);&lt;/span&gt;
          &lt;span class=&quot;n&quot;&gt;nextIndex&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;++;&lt;/span&gt;
          &lt;span class=&quot;n&quot;&gt;expectedModCount&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;++;&lt;/span&gt;
      &lt;span class=&quot;o&quot;&gt;}&lt;/span&gt;
      &lt;span class=&quot;nd&quot;&gt;@Override&lt;/span&gt;
      &lt;span class=&quot;kd&quot;&gt;public&lt;/span&gt; &lt;span class=&quot;kt&quot;&gt;boolean&lt;/span&gt; &lt;span class=&quot;nf&quot;&gt;hasNext&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;()&lt;/span&gt; &lt;span class=&quot;o&quot;&gt;{&lt;/span&gt;
          &lt;span class=&quot;k&quot;&gt;return&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;nextIndex&lt;/span&gt; &lt;span class=&quot;o&quot;&gt;&amp;lt;&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;size&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;;&lt;/span&gt;
      &lt;span class=&quot;o&quot;&gt;}&lt;/span&gt;
      &lt;span class=&quot;nd&quot;&gt;@Override&lt;/span&gt;
      &lt;span class=&quot;kd&quot;&gt;public&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;E&lt;/span&gt; &lt;span class=&quot;nf&quot;&gt;next&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;()&lt;/span&gt; &lt;span class=&quot;o&quot;&gt;{&lt;/span&gt;
          &lt;span class=&quot;c1&quot;&gt;//检查修改计数&lt;/span&gt;
          &lt;span class=&quot;n&quot;&gt;checkForComodification&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;();&lt;/span&gt;
          &lt;span class=&quot;k&quot;&gt;if&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;(!&lt;/span&gt;&lt;span class=&quot;n&quot;&gt;hasNext&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;())&lt;/span&gt;
              &lt;span class=&quot;k&quot;&gt;throw&lt;/span&gt; &lt;span class=&quot;k&quot;&gt;new&lt;/span&gt; &lt;span class=&quot;nf&quot;&gt;NoSuchElementException&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;();&lt;/span&gt;
          &lt;span class=&quot;n&quot;&gt;lastReturned&lt;/span&gt; &lt;span class=&quot;o&quot;&gt;=&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;next&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;;&lt;/span&gt;
          &lt;span class=&quot;n&quot;&gt;next&lt;/span&gt; &lt;span class=&quot;o&quot;&gt;=&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;next&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;.&lt;/span&gt;&lt;span class=&quot;na&quot;&gt;next&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;;&lt;/span&gt;
          &lt;span class=&quot;n&quot;&gt;nextIndex&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;++;&lt;/span&gt;
          &lt;span class=&quot;k&quot;&gt;return&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;lastReturned&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;.&lt;/span&gt;&lt;span class=&quot;na&quot;&gt;item&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;;&lt;/span&gt;
      &lt;span class=&quot;o&quot;&gt;}&lt;/span&gt;
      &lt;span class=&quot;nd&quot;&gt;@Override&lt;/span&gt;
      &lt;span class=&quot;kd&quot;&gt;public&lt;/span&gt; &lt;span class=&quot;kt&quot;&gt;boolean&lt;/span&gt; &lt;span class=&quot;nf&quot;&gt;hasPrevious&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;()&lt;/span&gt; &lt;span class=&quot;o&quot;&gt;{&lt;/span&gt;
          &lt;span class=&quot;c1&quot;&gt;//nextIndex时显然不能有prev&lt;/span&gt;
          &lt;span class=&quot;k&quot;&gt;return&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;nextIndex&lt;/span&gt; &lt;span class=&quot;o&quot;&gt;&amp;gt;&lt;/span&gt; &lt;span class=&quot;mi&quot;&gt;0&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;;&lt;/span&gt;
      &lt;span class=&quot;o&quot;&gt;}&lt;/span&gt;
      &lt;span class=&quot;c1&quot;&gt;//前一个结点，此时next和lastReturned值一致&lt;/span&gt;
      &lt;span class=&quot;nd&quot;&gt;@Override&lt;/span&gt;
      &lt;span class=&quot;kd&quot;&gt;public&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;E&lt;/span&gt; &lt;span class=&quot;nf&quot;&gt;previous&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;()&lt;/span&gt; &lt;span class=&quot;o&quot;&gt;{&lt;/span&gt;
          &lt;span class=&quot;n&quot;&gt;checkForComodification&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;();&lt;/span&gt;
          &lt;span class=&quot;k&quot;&gt;if&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;(!&lt;/span&gt;&lt;span class=&quot;n&quot;&gt;hasPrevious&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;())&lt;/span&gt;
              &lt;span class=&quot;k&quot;&gt;throw&lt;/span&gt; &lt;span class=&quot;k&quot;&gt;new&lt;/span&gt; &lt;span class=&quot;nf&quot;&gt;NoSuchElementException&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;();&lt;/span&gt;
          &lt;span class=&quot;n&quot;&gt;nextIndex&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;--;&lt;/span&gt;
          &lt;span class=&quot;n&quot;&gt;lastReturned&lt;/span&gt; &lt;span class=&quot;o&quot;&gt;=&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;next&lt;/span&gt; &lt;span class=&quot;o&quot;&gt;=&lt;/span&gt; &lt;span class=&quot;o&quot;&gt;(&lt;/span&gt;&lt;span class=&quot;n&quot;&gt;next&lt;/span&gt; &lt;span class=&quot;o&quot;&gt;==&lt;/span&gt; &lt;span class=&quot;kc&quot;&gt;null&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;)&lt;/span&gt; &lt;span class=&quot;o&quot;&gt;?&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;last&lt;/span&gt; &lt;span class=&quot;o&quot;&gt;:&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;next&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;.&lt;/span&gt;&lt;span class=&quot;na&quot;&gt;prev&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;;&lt;/span&gt;
          &lt;span class=&quot;k&quot;&gt;return&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;lastReturned&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;.&lt;/span&gt;&lt;span class=&quot;na&quot;&gt;item&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;;&lt;/span&gt;
      &lt;span class=&quot;o&quot;&gt;}&lt;/span&gt;
      &lt;span class=&quot;nd&quot;&gt;@Override&lt;/span&gt;
      &lt;span class=&quot;kd&quot;&gt;public&lt;/span&gt; &lt;span class=&quot;kt&quot;&gt;int&lt;/span&gt; &lt;span class=&quot;nf&quot;&gt;nextIndex&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;()&lt;/span&gt; &lt;span class=&quot;o&quot;&gt;{&lt;/span&gt;
          &lt;span class=&quot;k&quot;&gt;return&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;nextIndex&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;;&lt;/span&gt;
      &lt;span class=&quot;o&quot;&gt;}&lt;/span&gt;
      &lt;span class=&quot;nd&quot;&gt;@Override&lt;/span&gt;
      &lt;span class=&quot;kd&quot;&gt;public&lt;/span&gt; &lt;span class=&quot;kt&quot;&gt;int&lt;/span&gt; &lt;span class=&quot;nf&quot;&gt;previousIndex&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;()&lt;/span&gt; &lt;span class=&quot;o&quot;&gt;{&lt;/span&gt;
          &lt;span class=&quot;k&quot;&gt;return&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;nextIndex&lt;/span&gt; &lt;span class=&quot;o&quot;&gt;-&lt;/span&gt; &lt;span class=&quot;mi&quot;&gt;1&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;;&lt;/span&gt;
      &lt;span class=&quot;o&quot;&gt;}&lt;/span&gt;
      &lt;span class=&quot;c1&quot;&gt;//删除最后返回的结点&lt;/span&gt;
      &lt;span class=&quot;nd&quot;&gt;@Override&lt;/span&gt;
      &lt;span class=&quot;kd&quot;&gt;public&lt;/span&gt; &lt;span class=&quot;kt&quot;&gt;void&lt;/span&gt; &lt;span class=&quot;nf&quot;&gt;remove&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;()&lt;/span&gt; &lt;span class=&quot;o&quot;&gt;{&lt;/span&gt;
          &lt;span class=&quot;c1&quot;&gt;//检查修改计数&lt;/span&gt;
          &lt;span class=&quot;n&quot;&gt;checkForComodification&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;();&lt;/span&gt;
          &lt;span class=&quot;k&quot;&gt;if&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;(&lt;/span&gt;&lt;span class=&quot;n&quot;&gt;lastReturned&lt;/span&gt; &lt;span class=&quot;o&quot;&gt;==&lt;/span&gt; &lt;span class=&quot;kc&quot;&gt;null&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;)&lt;/span&gt;
              &lt;span class=&quot;k&quot;&gt;throw&lt;/span&gt; &lt;span class=&quot;k&quot;&gt;new&lt;/span&gt; &lt;span class=&quot;nf&quot;&gt;IllegalStateException&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;();&lt;/span&gt;

          &lt;span class=&quot;n&quot;&gt;Node&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;&amp;lt;&lt;/span&gt;&lt;span class=&quot;n&quot;&gt;E&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;&amp;gt;&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;lastNext&lt;/span&gt; &lt;span class=&quot;o&quot;&gt;=&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;lastReturned&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;.&lt;/span&gt;&lt;span class=&quot;na&quot;&gt;next&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;;&lt;/span&gt;
          &lt;span class=&quot;n&quot;&gt;unlink&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;(&lt;/span&gt;&lt;span class=&quot;n&quot;&gt;lastReturned&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;);&lt;/span&gt;
          &lt;span class=&quot;c1&quot;&gt;//如果next和lastReturned（这种情况在previous执行后出现），要修改next值&lt;/span&gt;
          &lt;span class=&quot;k&quot;&gt;if&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;(&lt;/span&gt;&lt;span class=&quot;n&quot;&gt;next&lt;/span&gt; &lt;span class=&quot;o&quot;&gt;==&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;lastReturned&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;)&lt;/span&gt;
              &lt;span class=&quot;n&quot;&gt;next&lt;/span&gt; &lt;span class=&quot;o&quot;&gt;=&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;lastNext&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;;&lt;/span&gt; &lt;span class=&quot;c1&quot;&gt;//虽然删除了一个结点，但是next向后移动了一位，因此nextIndex值不需要修改&lt;/span&gt;
          &lt;span class=&quot;k&quot;&gt;else&lt;/span&gt;
              &lt;span class=&quot;n&quot;&gt;nextIndex&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;--;&lt;/span&gt;
          &lt;span class=&quot;n&quot;&gt;lastReturned&lt;/span&gt; &lt;span class=&quot;o&quot;&gt;=&lt;/span&gt; &lt;span class=&quot;kc&quot;&gt;null&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;;&lt;/span&gt;
          &lt;span class=&quot;n&quot;&gt;expectedModCount&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;++;&lt;/span&gt;
      &lt;span class=&quot;o&quot;&gt;}&lt;/span&gt;
      &lt;span class=&quot;c1&quot;&gt;//修改最后返回结点的值&lt;/span&gt;
      &lt;span class=&quot;nd&quot;&gt;@Override&lt;/span&gt;
      &lt;span class=&quot;kd&quot;&gt;public&lt;/span&gt; &lt;span class=&quot;kt&quot;&gt;void&lt;/span&gt; &lt;span class=&quot;nf&quot;&gt;set&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;(&lt;/span&gt;&lt;span class=&quot;n&quot;&gt;E&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;e&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;)&lt;/span&gt; &lt;span class=&quot;o&quot;&gt;{&lt;/span&gt;
          &lt;span class=&quot;k&quot;&gt;if&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;(&lt;/span&gt;&lt;span class=&quot;n&quot;&gt;lastReturned&lt;/span&gt; &lt;span class=&quot;o&quot;&gt;==&lt;/span&gt; &lt;span class=&quot;kc&quot;&gt;null&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;)&lt;/span&gt;
              &lt;span class=&quot;k&quot;&gt;throw&lt;/span&gt; &lt;span class=&quot;k&quot;&gt;new&lt;/span&gt; &lt;span class=&quot;nf&quot;&gt;IllegalStateException&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;();&lt;/span&gt;
          &lt;span class=&quot;n&quot;&gt;checkForComodification&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;();&lt;/span&gt;
          &lt;span class=&quot;n&quot;&gt;lastReturned&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;.&lt;/span&gt;&lt;span class=&quot;na&quot;&gt;item&lt;/span&gt; &lt;span class=&quot;o&quot;&gt;=&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;e&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;;&lt;/span&gt;
      &lt;span class=&quot;o&quot;&gt;}&lt;/span&gt;
      &lt;span class=&quot;c1&quot;&gt;//检查是否并发修改&lt;/span&gt;
      &lt;span class=&quot;kd&quot;&gt;final&lt;/span&gt; &lt;span class=&quot;kt&quot;&gt;void&lt;/span&gt; &lt;span class=&quot;nf&quot;&gt;checkForComodification&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;()&lt;/span&gt; &lt;span class=&quot;o&quot;&gt;{&lt;/span&gt;
          &lt;span class=&quot;k&quot;&gt;if&lt;/span&gt; &lt;span class=&quot;o&quot;&gt;(&lt;/span&gt;&lt;span class=&quot;n&quot;&gt;modCount&lt;/span&gt; &lt;span class=&quot;o&quot;&gt;!=&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;expectedModCount&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;)&lt;/span&gt;
              &lt;span class=&quot;k&quot;&gt;throw&lt;/span&gt; &lt;span class=&quot;k&quot;&gt;new&lt;/span&gt; &lt;span class=&quot;nf&quot;&gt;ConcurrentModificationException&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;();&lt;/span&gt;
      &lt;span class=&quot;o&quot;&gt;}&lt;/span&gt;
  &lt;span class=&quot;o&quot;&gt;}&lt;/span&gt;
&lt;/code&gt;&lt;/pre&gt;
        &lt;/div&gt;
        &lt;ol&gt;
          &lt;li&gt;操作：LinkedList继承自AbstractSequentialList，实现了List，Deque，Serializable和Cloneable；因此可以按此顺序进行解释，首先分析LinkedList自身最很核心的方法。&lt;/li&gt;
        &lt;/ol&gt;
      &lt;/li&gt;
      &lt;li&gt;3-1  核心操作：包括linkFirst，linkLast，linkBefore，unlink，unlinkFirst，unlinkLast，node；这7个方法实现了双向链表最核心的功能，其他接口实现大部分是基于这7个方法的。
        &lt;ul&gt;
          &lt;li&gt;3-1-1. 这些方法有几个重要的细节：
            &lt;ul&gt;
              &lt;li&gt;i. 删除结点的时候置空操作；&lt;/li&gt;
              &lt;li&gt;ii. modCount的修改；&lt;/li&gt;
              &lt;li&gt;iii. node方法查找某个位置的结点根据index和size/2的关系进行优化处理；
                &lt;div class=&quot;language-java highlighter-rouge&quot;&gt;&lt;pre class=&quot;highlight&quot;&gt;&lt;code&gt;&lt;span class=&quot;c1&quot;&gt;//在头端插入&lt;/span&gt;
&lt;span class=&quot;kd&quot;&gt;private&lt;/span&gt; &lt;span class=&quot;kt&quot;&gt;void&lt;/span&gt; &lt;span class=&quot;nf&quot;&gt;linkFirst&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;(&lt;/span&gt;&lt;span class=&quot;n&quot;&gt;E&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;e&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;)&lt;/span&gt; &lt;span class=&quot;o&quot;&gt;{&lt;/span&gt;
  &lt;span class=&quot;kd&quot;&gt;final&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;Node&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;&amp;lt;&lt;/span&gt;&lt;span class=&quot;n&quot;&gt;E&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;&amp;gt;&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;f&lt;/span&gt; &lt;span class=&quot;o&quot;&gt;=&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;first&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;;&lt;/span&gt;
  &lt;span class=&quot;kd&quot;&gt;final&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;Node&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;&amp;lt;&lt;/span&gt;&lt;span class=&quot;n&quot;&gt;E&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;&amp;gt;&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;newNode&lt;/span&gt; &lt;span class=&quot;o&quot;&gt;=&lt;/span&gt; &lt;span class=&quot;k&quot;&gt;new&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;Node&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;&amp;lt;&amp;gt;(&lt;/span&gt;&lt;span class=&quot;n&quot;&gt;e&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;,&lt;/span&gt; &lt;span class=&quot;kc&quot;&gt;null&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;,&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;f&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;);&lt;/span&gt;
  &lt;span class=&quot;n&quot;&gt;first&lt;/span&gt; &lt;span class=&quot;o&quot;&gt;=&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;newNode&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;;&lt;/span&gt;
  &lt;span class=&quot;k&quot;&gt;if&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;(&lt;/span&gt;&lt;span class=&quot;n&quot;&gt;f&lt;/span&gt; &lt;span class=&quot;o&quot;&gt;==&lt;/span&gt; &lt;span class=&quot;kc&quot;&gt;null&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;)&lt;/span&gt; &lt;span class=&quot;o&quot;&gt;{&lt;/span&gt;
      &lt;span class=&quot;c1&quot;&gt;//原链表为空时last指针也要指向新结点&lt;/span&gt;
      &lt;span class=&quot;n&quot;&gt;last&lt;/span&gt; &lt;span class=&quot;o&quot;&gt;=&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;newNode&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;;&lt;/span&gt;
  &lt;span class=&quot;o&quot;&gt;}&lt;/span&gt; &lt;span class=&quot;k&quot;&gt;else&lt;/span&gt; &lt;span class=&quot;o&quot;&gt;{&lt;/span&gt;
      &lt;span class=&quot;n&quot;&gt;f&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;.&lt;/span&gt;&lt;span class=&quot;na&quot;&gt;prev&lt;/span&gt; &lt;span class=&quot;o&quot;&gt;=&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;newNode&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;;&lt;/span&gt;
  &lt;span class=&quot;o&quot;&gt;}&lt;/span&gt;
  &lt;span class=&quot;o&quot;&gt;++&lt;/span&gt;&lt;span class=&quot;n&quot;&gt;size&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;;&lt;/span&gt;
  &lt;span class=&quot;c1&quot;&gt;//增加修改次数&lt;/span&gt;
  &lt;span class=&quot;o&quot;&gt;++&lt;/span&gt;&lt;span class=&quot;n&quot;&gt;modCount&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;;&lt;/span&gt;
&lt;span class=&quot;o&quot;&gt;}&lt;/span&gt;
&lt;span class=&quot;c1&quot;&gt;//在尾端插入&lt;/span&gt;
&lt;span class=&quot;kt&quot;&gt;void&lt;/span&gt; &lt;span class=&quot;nf&quot;&gt;linkLast&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;(&lt;/span&gt;&lt;span class=&quot;n&quot;&gt;E&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;e&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;)&lt;/span&gt; &lt;span class=&quot;o&quot;&gt;{&lt;/span&gt;
  &lt;span class=&quot;kd&quot;&gt;final&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;Node&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;&amp;lt;&lt;/span&gt;&lt;span class=&quot;n&quot;&gt;E&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;&amp;gt;&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;l&lt;/span&gt; &lt;span class=&quot;o&quot;&gt;=&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;last&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;;&lt;/span&gt;
  &lt;span class=&quot;kd&quot;&gt;final&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;Node&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;&amp;lt;&lt;/span&gt;&lt;span class=&quot;n&quot;&gt;E&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;&amp;gt;&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;newNode&lt;/span&gt; &lt;span class=&quot;o&quot;&gt;=&lt;/span&gt; &lt;span class=&quot;k&quot;&gt;new&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;Node&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;&amp;lt;&amp;gt;(&lt;/span&gt;&lt;span class=&quot;n&quot;&gt;e&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;,&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;l&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;,&lt;/span&gt; &lt;span class=&quot;kc&quot;&gt;null&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;);&lt;/span&gt;
  &lt;span class=&quot;n&quot;&gt;last&lt;/span&gt; &lt;span class=&quot;o&quot;&gt;=&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;newNode&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;;&lt;/span&gt;
  &lt;span class=&quot;k&quot;&gt;if&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;(&lt;/span&gt;&lt;span class=&quot;n&quot;&gt;l&lt;/span&gt; &lt;span class=&quot;o&quot;&gt;==&lt;/span&gt; &lt;span class=&quot;kc&quot;&gt;null&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;)&lt;/span&gt; &lt;span class=&quot;o&quot;&gt;{&lt;/span&gt;
      &lt;span class=&quot;c1&quot;&gt;//原链表为空时first指针也要执行新结点&lt;/span&gt;
      &lt;span class=&quot;n&quot;&gt;first&lt;/span&gt; &lt;span class=&quot;o&quot;&gt;=&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;newNode&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;;&lt;/span&gt;
  &lt;span class=&quot;o&quot;&gt;}&lt;/span&gt; &lt;span class=&quot;k&quot;&gt;else&lt;/span&gt; &lt;span class=&quot;o&quot;&gt;{&lt;/span&gt;
      &lt;span class=&quot;n&quot;&gt;l&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;.&lt;/span&gt;&lt;span class=&quot;na&quot;&gt;next&lt;/span&gt; &lt;span class=&quot;o&quot;&gt;=&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;newNode&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;;&lt;/span&gt;
  &lt;span class=&quot;o&quot;&gt;}&lt;/span&gt;
  &lt;span class=&quot;o&quot;&gt;++&lt;/span&gt;&lt;span class=&quot;n&quot;&gt;size&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;;&lt;/span&gt;
  &lt;span class=&quot;o&quot;&gt;++&lt;/span&gt;&lt;span class=&quot;n&quot;&gt;modCount&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;;&lt;/span&gt;
&lt;span class=&quot;o&quot;&gt;}&lt;/span&gt;
&lt;span class=&quot;c1&quot;&gt;//在指定结点前插入&lt;/span&gt;
&lt;span class=&quot;kt&quot;&gt;void&lt;/span&gt; &lt;span class=&quot;nf&quot;&gt;linkBefore&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;(&lt;/span&gt;&lt;span class=&quot;n&quot;&gt;E&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;e&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;,&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;Node&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;&amp;lt;&lt;/span&gt;&lt;span class=&quot;n&quot;&gt;E&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;&amp;gt;&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;succ&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;)&lt;/span&gt; &lt;span class=&quot;o&quot;&gt;{&lt;/span&gt;
  &lt;span class=&quot;kd&quot;&gt;final&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;Node&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;&amp;lt;&lt;/span&gt;&lt;span class=&quot;n&quot;&gt;E&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;&amp;gt;&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;pred&lt;/span&gt; &lt;span class=&quot;o&quot;&gt;=&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;succ&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;.&lt;/span&gt;&lt;span class=&quot;na&quot;&gt;prev&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;;&lt;/span&gt;
  &lt;span class=&quot;kd&quot;&gt;final&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;Node&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;&amp;lt;&lt;/span&gt;&lt;span class=&quot;n&quot;&gt;E&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;&amp;gt;&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;newNode&lt;/span&gt; &lt;span class=&quot;o&quot;&gt;=&lt;/span&gt; &lt;span class=&quot;k&quot;&gt;new&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;Node&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;&amp;lt;&amp;gt;(&lt;/span&gt;&lt;span class=&quot;n&quot;&gt;e&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;,&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;succ&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;.&lt;/span&gt;&lt;span class=&quot;na&quot;&gt;prev&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;,&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;succ&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;);&lt;/span&gt;
  &lt;span class=&quot;n&quot;&gt;succ&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;.&lt;/span&gt;&lt;span class=&quot;na&quot;&gt;prev&lt;/span&gt; &lt;span class=&quot;o&quot;&gt;=&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;newNode&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;;&lt;/span&gt;
  &lt;span class=&quot;k&quot;&gt;if&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;(&lt;/span&gt;&lt;span class=&quot;n&quot;&gt;pred&lt;/span&gt; &lt;span class=&quot;o&quot;&gt;==&lt;/span&gt; &lt;span class=&quot;kc&quot;&gt;null&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;)&lt;/span&gt; &lt;span class=&quot;o&quot;&gt;{&lt;/span&gt;
      &lt;span class=&quot;n&quot;&gt;first&lt;/span&gt; &lt;span class=&quot;o&quot;&gt;=&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;newNode&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;;&lt;/span&gt;
  &lt;span class=&quot;o&quot;&gt;}&lt;/span&gt; &lt;span class=&quot;k&quot;&gt;else&lt;/span&gt; &lt;span class=&quot;o&quot;&gt;{&lt;/span&gt;
      &lt;span class=&quot;n&quot;&gt;pred&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;.&lt;/span&gt;&lt;span class=&quot;na&quot;&gt;next&lt;/span&gt; &lt;span class=&quot;o&quot;&gt;=&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;newNode&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;;&lt;/span&gt;
  &lt;span class=&quot;o&quot;&gt;}&lt;/span&gt;
  &lt;span class=&quot;o&quot;&gt;++&lt;/span&gt;&lt;span class=&quot;n&quot;&gt;size&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;;&lt;/span&gt;
  &lt;span class=&quot;o&quot;&gt;++&lt;/span&gt;&lt;span class=&quot;n&quot;&gt;modCount&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;;&lt;/span&gt;
&lt;span class=&quot;o&quot;&gt;}&lt;/span&gt;
&lt;span class=&quot;c1&quot;&gt;//删除第一个结点，由调用者判断是否有头结点&lt;/span&gt;
&lt;span class=&quot;kd&quot;&gt;private&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;E&lt;/span&gt; &lt;span class=&quot;nf&quot;&gt;unlinkFirst&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;(&lt;/span&gt;&lt;span class=&quot;n&quot;&gt;Node&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;&amp;lt;&lt;/span&gt;&lt;span class=&quot;n&quot;&gt;E&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;&amp;gt;&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;f&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;)&lt;/span&gt; &lt;span class=&quot;o&quot;&gt;{&lt;/span&gt;
  &lt;span class=&quot;kd&quot;&gt;final&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;E&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;element&lt;/span&gt; &lt;span class=&quot;o&quot;&gt;=&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;f&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;.&lt;/span&gt;&lt;span class=&quot;na&quot;&gt;item&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;;&lt;/span&gt;
  &lt;span class=&quot;kd&quot;&gt;final&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;Node&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;&amp;lt;&lt;/span&gt;&lt;span class=&quot;n&quot;&gt;E&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;&amp;gt;&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;next&lt;/span&gt; &lt;span class=&quot;o&quot;&gt;=&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;f&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;.&lt;/span&gt;&lt;span class=&quot;na&quot;&gt;next&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;;&lt;/span&gt;
  &lt;span class=&quot;n&quot;&gt;f&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;.&lt;/span&gt;&lt;span class=&quot;na&quot;&gt;next&lt;/span&gt; &lt;span class=&quot;o&quot;&gt;=&lt;/span&gt; &lt;span class=&quot;kc&quot;&gt;null&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;;&lt;/span&gt; &lt;span class=&quot;c1&quot;&gt;//删除之后置为null，不影响被引用对象的垃圾回收&lt;/span&gt;
  &lt;span class=&quot;n&quot;&gt;f&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;.&lt;/span&gt;&lt;span class=&quot;na&quot;&gt;item&lt;/span&gt; &lt;span class=&quot;o&quot;&gt;=&lt;/span&gt; &lt;span class=&quot;kc&quot;&gt;null&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;;&lt;/span&gt;
  &lt;span class=&quot;n&quot;&gt;first&lt;/span&gt; &lt;span class=&quot;o&quot;&gt;=&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;next&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;;&lt;/span&gt; &lt;span class=&quot;c1&quot;&gt;//first指针指向next&lt;/span&gt;
  &lt;span class=&quot;k&quot;&gt;if&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;(&lt;/span&gt;&lt;span class=&quot;n&quot;&gt;next&lt;/span&gt; &lt;span class=&quot;o&quot;&gt;==&lt;/span&gt; &lt;span class=&quot;kc&quot;&gt;null&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;)&lt;/span&gt;
      &lt;span class=&quot;n&quot;&gt;last&lt;/span&gt; &lt;span class=&quot;o&quot;&gt;=&lt;/span&gt; &lt;span class=&quot;kc&quot;&gt;null&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;;&lt;/span&gt;
  &lt;span class=&quot;k&quot;&gt;else&lt;/span&gt;
      &lt;span class=&quot;n&quot;&gt;next&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;.&lt;/span&gt;&lt;span class=&quot;na&quot;&gt;prev&lt;/span&gt; &lt;span class=&quot;o&quot;&gt;=&lt;/span&gt; &lt;span class=&quot;kc&quot;&gt;null&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;;&lt;/span&gt;
  &lt;span class=&quot;o&quot;&gt;--&lt;/span&gt;&lt;span class=&quot;n&quot;&gt;size&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;;&lt;/span&gt; &lt;span class=&quot;c1&quot;&gt;//数量减少&lt;/span&gt;
  &lt;span class=&quot;o&quot;&gt;++&lt;/span&gt;&lt;span class=&quot;n&quot;&gt;modCount&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;;&lt;/span&gt; &lt;span class=&quot;c1&quot;&gt;//修改计数增加&lt;/span&gt;
  &lt;span class=&quot;k&quot;&gt;return&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;element&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;;&lt;/span&gt;
&lt;span class=&quot;o&quot;&gt;}&lt;/span&gt;
&lt;span class=&quot;c1&quot;&gt;//删除最后一个结点&lt;/span&gt;
&lt;span class=&quot;kd&quot;&gt;private&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;E&lt;/span&gt; &lt;span class=&quot;nf&quot;&gt;unlinkLast&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;(&lt;/span&gt;&lt;span class=&quot;n&quot;&gt;Node&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;&amp;lt;&lt;/span&gt;&lt;span class=&quot;n&quot;&gt;E&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;&amp;gt;&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;l&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;)&lt;/span&gt; &lt;span class=&quot;o&quot;&gt;{&lt;/span&gt;
  &lt;span class=&quot;kd&quot;&gt;final&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;E&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;element&lt;/span&gt; &lt;span class=&quot;o&quot;&gt;=&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;l&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;.&lt;/span&gt;&lt;span class=&quot;na&quot;&gt;item&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;;&lt;/span&gt;
  &lt;span class=&quot;kd&quot;&gt;final&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;Node&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;&amp;lt;&lt;/span&gt;&lt;span class=&quot;n&quot;&gt;E&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;&amp;gt;&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;prev&lt;/span&gt; &lt;span class=&quot;o&quot;&gt;=&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;l&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;.&lt;/span&gt;&lt;span class=&quot;na&quot;&gt;prev&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;;&lt;/span&gt;
  &lt;span class=&quot;n&quot;&gt;l&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;.&lt;/span&gt;&lt;span class=&quot;na&quot;&gt;item&lt;/span&gt; &lt;span class=&quot;o&quot;&gt;=&lt;/span&gt; &lt;span class=&quot;kc&quot;&gt;null&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;;&lt;/span&gt; &lt;span class=&quot;c1&quot;&gt;//置空不影响原被引用对象的垃圾回收&lt;/span&gt;
  &lt;span class=&quot;n&quot;&gt;l&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;.&lt;/span&gt;&lt;span class=&quot;na&quot;&gt;prev&lt;/span&gt; &lt;span class=&quot;o&quot;&gt;=&lt;/span&gt; &lt;span class=&quot;kc&quot;&gt;null&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;;&lt;/span&gt;
  &lt;span class=&quot;n&quot;&gt;last&lt;/span&gt; &lt;span class=&quot;o&quot;&gt;=&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;prev&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;;&lt;/span&gt;
  &lt;span class=&quot;k&quot;&gt;if&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;(&lt;/span&gt;&lt;span class=&quot;n&quot;&gt;prev&lt;/span&gt; &lt;span class=&quot;o&quot;&gt;==&lt;/span&gt; &lt;span class=&quot;kc&quot;&gt;null&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;)&lt;/span&gt;
      &lt;span class=&quot;n&quot;&gt;first&lt;/span&gt; &lt;span class=&quot;o&quot;&gt;=&lt;/span&gt; &lt;span class=&quot;kc&quot;&gt;null&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;;&lt;/span&gt;
  &lt;span class=&quot;k&quot;&gt;else&lt;/span&gt;
      &lt;span class=&quot;n&quot;&gt;prev&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;.&lt;/span&gt;&lt;span class=&quot;na&quot;&gt;next&lt;/span&gt; &lt;span class=&quot;o&quot;&gt;=&lt;/span&gt; &lt;span class=&quot;kc&quot;&gt;null&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;;&lt;/span&gt;
  &lt;span class=&quot;o&quot;&gt;--&lt;/span&gt;&lt;span class=&quot;n&quot;&gt;size&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;;&lt;/span&gt;
  &lt;span class=&quot;o&quot;&gt;++&lt;/span&gt;&lt;span class=&quot;n&quot;&gt;modCount&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;;&lt;/span&gt;
  &lt;span class=&quot;k&quot;&gt;return&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;element&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;;&lt;/span&gt;
&lt;span class=&quot;o&quot;&gt;}&lt;/span&gt;
&lt;span class=&quot;c1&quot;&gt;//删除链表中某个结点&lt;/span&gt;
&lt;span class=&quot;n&quot;&gt;E&lt;/span&gt; &lt;span class=&quot;nf&quot;&gt;unlink&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;(&lt;/span&gt;&lt;span class=&quot;n&quot;&gt;Node&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;&amp;lt;&lt;/span&gt;&lt;span class=&quot;n&quot;&gt;E&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;&amp;gt;&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;x&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;)&lt;/span&gt; &lt;span class=&quot;o&quot;&gt;{&lt;/span&gt;
  &lt;span class=&quot;kd&quot;&gt;final&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;E&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;element&lt;/span&gt; &lt;span class=&quot;o&quot;&gt;=&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;x&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;.&lt;/span&gt;&lt;span class=&quot;na&quot;&gt;item&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;;&lt;/span&gt;
  &lt;span class=&quot;kd&quot;&gt;final&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;Node&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;&amp;lt;&lt;/span&gt;&lt;span class=&quot;n&quot;&gt;E&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;&amp;gt;&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;prev&lt;/span&gt; &lt;span class=&quot;o&quot;&gt;=&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;x&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;.&lt;/span&gt;&lt;span class=&quot;na&quot;&gt;prev&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;;&lt;/span&gt;
  &lt;span class=&quot;kd&quot;&gt;final&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;Node&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;&amp;lt;&lt;/span&gt;&lt;span class=&quot;n&quot;&gt;E&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;&amp;gt;&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;next&lt;/span&gt; &lt;span class=&quot;o&quot;&gt;=&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;x&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;.&lt;/span&gt;&lt;span class=&quot;na&quot;&gt;next&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;;&lt;/span&gt;
  &lt;span class=&quot;n&quot;&gt;x&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;.&lt;/span&gt;&lt;span class=&quot;na&quot;&gt;item&lt;/span&gt; &lt;span class=&quot;o&quot;&gt;=&lt;/span&gt; &lt;span class=&quot;kc&quot;&gt;null&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;;&lt;/span&gt; &lt;span class=&quot;c1&quot;&gt;//置空，不影响垃圾回收&lt;/span&gt;
  &lt;span class=&quot;k&quot;&gt;if&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;(&lt;/span&gt;&lt;span class=&quot;n&quot;&gt;prev&lt;/span&gt; &lt;span class=&quot;o&quot;&gt;==&lt;/span&gt; &lt;span class=&quot;kc&quot;&gt;null&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;)&lt;/span&gt;
      &lt;span class=&quot;n&quot;&gt;first&lt;/span&gt; &lt;span class=&quot;o&quot;&gt;=&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;next&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;;&lt;/span&gt;
  &lt;span class=&quot;k&quot;&gt;else&lt;/span&gt; &lt;span class=&quot;o&quot;&gt;{&lt;/span&gt;
      &lt;span class=&quot;n&quot;&gt;prev&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;.&lt;/span&gt;&lt;span class=&quot;na&quot;&gt;next&lt;/span&gt; &lt;span class=&quot;o&quot;&gt;=&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;next&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;;&lt;/span&gt;
      &lt;span class=&quot;n&quot;&gt;x&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;.&lt;/span&gt;&lt;span class=&quot;na&quot;&gt;prev&lt;/span&gt; &lt;span class=&quot;o&quot;&gt;=&lt;/span&gt; &lt;span class=&quot;kc&quot;&gt;null&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;;&lt;/span&gt;
  &lt;span class=&quot;o&quot;&gt;}&lt;/span&gt;
  &lt;span class=&quot;k&quot;&gt;if&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;(&lt;/span&gt;&lt;span class=&quot;n&quot;&gt;next&lt;/span&gt; &lt;span class=&quot;o&quot;&gt;==&lt;/span&gt; &lt;span class=&quot;kc&quot;&gt;null&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;)&lt;/span&gt;
      &lt;span class=&quot;n&quot;&gt;last&lt;/span&gt; &lt;span class=&quot;o&quot;&gt;=&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;prev&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;;&lt;/span&gt;
  &lt;span class=&quot;k&quot;&gt;else&lt;/span&gt; &lt;span class=&quot;o&quot;&gt;{&lt;/span&gt;
      &lt;span class=&quot;n&quot;&gt;next&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;.&lt;/span&gt;&lt;span class=&quot;na&quot;&gt;prev&lt;/span&gt; &lt;span class=&quot;o&quot;&gt;=&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;prev&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;;&lt;/span&gt;
      &lt;span class=&quot;n&quot;&gt;x&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;.&lt;/span&gt;&lt;span class=&quot;na&quot;&gt;next&lt;/span&gt; &lt;span class=&quot;o&quot;&gt;=&lt;/span&gt; &lt;span class=&quot;kc&quot;&gt;null&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;;&lt;/span&gt;
  &lt;span class=&quot;o&quot;&gt;}&lt;/span&gt;
  &lt;span class=&quot;o&quot;&gt;--&lt;/span&gt;&lt;span class=&quot;n&quot;&gt;size&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;;&lt;/span&gt;
  &lt;span class=&quot;o&quot;&gt;++&lt;/span&gt;&lt;span class=&quot;n&quot;&gt;modCount&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;;&lt;/span&gt;
  &lt;span class=&quot;k&quot;&gt;return&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;element&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;;&lt;/span&gt;
&lt;span class=&quot;o&quot;&gt;}&lt;/span&gt;
&lt;span class=&quot;c1&quot;&gt;//获取指定位置的结点，通过index是否小于size/2进行优化&lt;/span&gt;
&lt;span class=&quot;n&quot;&gt;Node&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;&amp;lt;&lt;/span&gt;&lt;span class=&quot;n&quot;&gt;E&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;&amp;gt;&lt;/span&gt; &lt;span class=&quot;nf&quot;&gt;node&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;(&lt;/span&gt;&lt;span class=&quot;kt&quot;&gt;int&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;index&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;)&lt;/span&gt; &lt;span class=&quot;o&quot;&gt;{&lt;/span&gt;
  &lt;span class=&quot;c1&quot;&gt;//如果小于size / 2从头开始搜索，否则从尾开始搜索&lt;/span&gt;
  &lt;span class=&quot;k&quot;&gt;if&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;(&lt;/span&gt;&lt;span class=&quot;n&quot;&gt;index&lt;/span&gt; &lt;span class=&quot;o&quot;&gt;&amp;lt;&lt;/span&gt; &lt;span class=&quot;o&quot;&gt;(&lt;/span&gt;&lt;span class=&quot;n&quot;&gt;size&lt;/span&gt; &lt;span class=&quot;o&quot;&gt;&amp;gt;&amp;gt;&lt;/span&gt; &lt;span class=&quot;mi&quot;&gt;1&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;))&lt;/span&gt; &lt;span class=&quot;o&quot;&gt;{&lt;/span&gt;
      &lt;span class=&quot;n&quot;&gt;Node&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;&amp;lt;&lt;/span&gt;&lt;span class=&quot;n&quot;&gt;E&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;&amp;gt;&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;x&lt;/span&gt; &lt;span class=&quot;o&quot;&gt;=&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;first&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;;&lt;/span&gt;
      &lt;span class=&quot;k&quot;&gt;for&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;(&lt;/span&gt;&lt;span class=&quot;kt&quot;&gt;int&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;i&lt;/span&gt; &lt;span class=&quot;o&quot;&gt;=&lt;/span&gt; &lt;span class=&quot;mi&quot;&gt;0&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;;&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;i&lt;/span&gt; &lt;span class=&quot;o&quot;&gt;&amp;lt;&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;index&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;;&lt;/span&gt; &lt;span class=&quot;o&quot;&gt;++&lt;/span&gt;&lt;span class=&quot;n&quot;&gt;i&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;)&lt;/span&gt;
          &lt;span class=&quot;n&quot;&gt;x&lt;/span&gt; &lt;span class=&quot;o&quot;&gt;=&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;x&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;.&lt;/span&gt;&lt;span class=&quot;na&quot;&gt;next&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;;&lt;/span&gt;
      &lt;span class=&quot;k&quot;&gt;return&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;x&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;;&lt;/span&gt;
  &lt;span class=&quot;o&quot;&gt;}&lt;/span&gt; &lt;span class=&quot;k&quot;&gt;else&lt;/span&gt; &lt;span class=&quot;o&quot;&gt;{&lt;/span&gt;
      &lt;span class=&quot;n&quot;&gt;Node&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;&amp;lt;&lt;/span&gt;&lt;span class=&quot;n&quot;&gt;E&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;&amp;gt;&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;x&lt;/span&gt; &lt;span class=&quot;o&quot;&gt;=&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;last&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;;&lt;/span&gt;
      &lt;span class=&quot;k&quot;&gt;for&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;(&lt;/span&gt;&lt;span class=&quot;kt&quot;&gt;int&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;i&lt;/span&gt; &lt;span class=&quot;o&quot;&gt;=&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;size&lt;/span&gt; &lt;span class=&quot;o&quot;&gt;-&lt;/span&gt; &lt;span class=&quot;mi&quot;&gt;1&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;;&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;i&lt;/span&gt; &lt;span class=&quot;o&quot;&gt;&amp;gt;=&lt;/span&gt; &lt;span class=&quot;mi&quot;&gt;0&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;;&lt;/span&gt; &lt;span class=&quot;o&quot;&gt;--&lt;/span&gt;&lt;span class=&quot;n&quot;&gt;i&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;)&lt;/span&gt;
          &lt;span class=&quot;n&quot;&gt;x&lt;/span&gt; &lt;span class=&quot;o&quot;&gt;=&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;x&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;.&lt;/span&gt;&lt;span class=&quot;na&quot;&gt;prev&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;;&lt;/span&gt;
      &lt;span class=&quot;k&quot;&gt;return&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;x&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;;&lt;/span&gt;
  &lt;span class=&quot;o&quot;&gt;}&lt;/span&gt;
&lt;span class=&quot;o&quot;&gt;}&lt;/span&gt;
&lt;/code&gt;&lt;/pre&gt;
                &lt;/div&gt;
              &lt;/li&gt;
            &lt;/ul&gt;
          &lt;/li&gt;
        &lt;/ul&gt;
      &lt;/li&gt;
    &lt;/ul&gt;
  &lt;/li&gt;
  &lt;li&gt;3-2 私有辅助方法：包括检查查找索引，插入位置是否合法；
    &lt;div class=&quot;language-java highlighter-rouge&quot;&gt;&lt;pre class=&quot;highlight&quot;&gt;&lt;code&gt;    &lt;span class=&quot;c1&quot;&gt;//检查索引是否合法&lt;/span&gt;
    &lt;span class=&quot;kd&quot;&gt;private&lt;/span&gt; &lt;span class=&quot;kt&quot;&gt;boolean&lt;/span&gt; &lt;span class=&quot;nf&quot;&gt;isElementIndex&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;(&lt;/span&gt;&lt;span class=&quot;kt&quot;&gt;int&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;index&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;)&lt;/span&gt; &lt;span class=&quot;o&quot;&gt;{&lt;/span&gt;
        &lt;span class=&quot;k&quot;&gt;return&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;index&lt;/span&gt; &lt;span class=&quot;o&quot;&gt;&amp;gt;=&lt;/span&gt; &lt;span class=&quot;mi&quot;&gt;0&lt;/span&gt; &lt;span class=&quot;o&quot;&gt;&amp;amp;&amp;amp;&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;index&lt;/span&gt; &lt;span class=&quot;o&quot;&gt;&amp;lt;&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;size&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;;&lt;/span&gt;
    &lt;span class=&quot;o&quot;&gt;}&lt;/span&gt;
    &lt;span class=&quot;c1&quot;&gt;//检查索引是否合法，不合法抛出异常&lt;/span&gt;
    &lt;span class=&quot;kd&quot;&gt;private&lt;/span&gt; &lt;span class=&quot;kt&quot;&gt;void&lt;/span&gt; &lt;span class=&quot;nf&quot;&gt;checkElementIndex&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;(&lt;/span&gt;&lt;span class=&quot;kt&quot;&gt;int&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;index&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;)&lt;/span&gt; &lt;span class=&quot;o&quot;&gt;{&lt;/span&gt;
        &lt;span class=&quot;k&quot;&gt;if&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;(&lt;/span&gt;&lt;span class=&quot;n&quot;&gt;isElementIndex&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;(&lt;/span&gt;&lt;span class=&quot;n&quot;&gt;index&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;))&lt;/span&gt;
            &lt;span class=&quot;k&quot;&gt;throw&lt;/span&gt; &lt;span class=&quot;k&quot;&gt;new&lt;/span&gt; &lt;span class=&quot;nf&quot;&gt;IndexOutOfBoundsException&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;(&lt;/span&gt;&lt;span class=&quot;n&quot;&gt;outOfBoundsMsg&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;(&lt;/span&gt;&lt;span class=&quot;n&quot;&gt;index&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;));&lt;/span&gt;
    &lt;span class=&quot;o&quot;&gt;}&lt;/span&gt;
    &lt;span class=&quot;kd&quot;&gt;private&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;String&lt;/span&gt; &lt;span class=&quot;nf&quot;&gt;outOfBoundsMsg&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;(&lt;/span&gt;&lt;span class=&quot;kt&quot;&gt;int&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;index&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;)&lt;/span&gt; &lt;span class=&quot;o&quot;&gt;{&lt;/span&gt;
        &lt;span class=&quot;k&quot;&gt;return&lt;/span&gt; &lt;span class=&quot;s&quot;&gt;&quot;Index: &quot;&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;+&lt;/span&gt;&lt;span class=&quot;n&quot;&gt;index&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;+&lt;/span&gt;&lt;span class=&quot;s&quot;&gt;&quot;, Size: &quot;&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;+&lt;/span&gt;&lt;span class=&quot;n&quot;&gt;size&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;;&lt;/span&gt;
    &lt;span class=&quot;o&quot;&gt;}&lt;/span&gt;
    &lt;span class=&quot;c1&quot;&gt;//检查待插入位置的索引值是否合法&lt;/span&gt;
    &lt;span class=&quot;kd&quot;&gt;private&lt;/span&gt; &lt;span class=&quot;kt&quot;&gt;boolean&lt;/span&gt; &lt;span class=&quot;nf&quot;&gt;isPositionIndex&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;(&lt;/span&gt;&lt;span class=&quot;kt&quot;&gt;int&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;index&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;)&lt;/span&gt; &lt;span class=&quot;o&quot;&gt;{&lt;/span&gt;
        &lt;span class=&quot;k&quot;&gt;return&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;index&lt;/span&gt; &lt;span class=&quot;o&quot;&gt;&amp;gt;=&lt;/span&gt; &lt;span class=&quot;mi&quot;&gt;0&lt;/span&gt; &lt;span class=&quot;o&quot;&gt;&amp;amp;&amp;amp;&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;index&lt;/span&gt; &lt;span class=&quot;o&quot;&gt;&amp;lt;=&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;size&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;;&lt;/span&gt;
    &lt;span class=&quot;o&quot;&gt;}&lt;/span&gt;
    &lt;span class=&quot;c1&quot;&gt;//检查待插入位置的索引值是否合法，不合法抛出异常&lt;/span&gt;
    &lt;span class=&quot;kd&quot;&gt;private&lt;/span&gt; &lt;span class=&quot;kt&quot;&gt;void&lt;/span&gt; &lt;span class=&quot;nf&quot;&gt;checkPositionIndex&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;(&lt;/span&gt;&lt;span class=&quot;kt&quot;&gt;int&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;index&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;)&lt;/span&gt; &lt;span class=&quot;o&quot;&gt;{&lt;/span&gt;
        &lt;span class=&quot;k&quot;&gt;if&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;(&lt;/span&gt;&lt;span class=&quot;n&quot;&gt;isPositionIndex&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;(&lt;/span&gt;&lt;span class=&quot;n&quot;&gt;index&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;))&lt;/span&gt;
            &lt;span class=&quot;k&quot;&gt;throw&lt;/span&gt; &lt;span class=&quot;k&quot;&gt;new&lt;/span&gt; &lt;span class=&quot;nf&quot;&gt;IndexOutOfBoundsException&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;(&lt;/span&gt;&lt;span class=&quot;n&quot;&gt;outOfBoundsMsg&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;(&lt;/span&gt;&lt;span class=&quot;n&quot;&gt;index&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;));&lt;/span&gt;
    &lt;span class=&quot;o&quot;&gt;}&lt;/span&gt;
&lt;/code&gt;&lt;/pre&gt;
    &lt;/div&gt;
  &lt;/li&gt;
  &lt;li&gt;3-3 List接口实现
    &lt;ul&gt;
      &lt;li&gt;3-3-1 基于Node内部表示，因此List的关键方法也要依赖与内部表示；&lt;/li&gt;
      &lt;li&gt;3-3-2 注意，LinkedList的subList实现没有覆盖AbstractList的实现；
        &lt;div class=&quot;language-java highlighter-rouge&quot;&gt;&lt;pre class=&quot;highlight&quot;&gt;&lt;code&gt;  &lt;span class=&quot;c1&quot;&gt;//添加结点，在表尾&lt;/span&gt;
  &lt;span class=&quot;nd&quot;&gt;@Override&lt;/span&gt;
  &lt;span class=&quot;kd&quot;&gt;public&lt;/span&gt; &lt;span class=&quot;kt&quot;&gt;boolean&lt;/span&gt; &lt;span class=&quot;nf&quot;&gt;add&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;(&lt;/span&gt;&lt;span class=&quot;n&quot;&gt;E&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;e&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;)&lt;/span&gt; &lt;span class=&quot;o&quot;&gt;{&lt;/span&gt;
      &lt;span class=&quot;n&quot;&gt;linkLast&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;(&lt;/span&gt;&lt;span class=&quot;n&quot;&gt;e&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;);&lt;/span&gt;
      &lt;span class=&quot;k&quot;&gt;return&lt;/span&gt; &lt;span class=&quot;kc&quot;&gt;true&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;;&lt;/span&gt;
  &lt;span class=&quot;o&quot;&gt;}&lt;/span&gt;
  &lt;span class=&quot;c1&quot;&gt;//在指定位置添加结点&lt;/span&gt;
  &lt;span class=&quot;nd&quot;&gt;@Override&lt;/span&gt;
  &lt;span class=&quot;kd&quot;&gt;public&lt;/span&gt; &lt;span class=&quot;kt&quot;&gt;void&lt;/span&gt; &lt;span class=&quot;nf&quot;&gt;add&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;(&lt;/span&gt;&lt;span class=&quot;kt&quot;&gt;int&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;index&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;,&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;E&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;element&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;)&lt;/span&gt; &lt;span class=&quot;o&quot;&gt;{&lt;/span&gt;
      &lt;span class=&quot;c1&quot;&gt;//检查插入位置是否合法&lt;/span&gt;
      &lt;span class=&quot;n&quot;&gt;checkPositionIndex&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;(&lt;/span&gt;&lt;span class=&quot;n&quot;&gt;index&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;);&lt;/span&gt;

      &lt;span class=&quot;k&quot;&gt;if&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;(&lt;/span&gt;&lt;span class=&quot;n&quot;&gt;index&lt;/span&gt; &lt;span class=&quot;o&quot;&gt;==&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;size&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;)&lt;/span&gt; &lt;span class=&quot;c1&quot;&gt;//排除为空的可能&lt;/span&gt;
          &lt;span class=&quot;n&quot;&gt;linkLast&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;(&lt;/span&gt;&lt;span class=&quot;n&quot;&gt;element&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;);&lt;/span&gt;
      &lt;span class=&quot;k&quot;&gt;else&lt;/span&gt; &lt;span class=&quot;o&quot;&gt;{&lt;/span&gt; &lt;span class=&quot;c1&quot;&gt;//index &amp;lt; size时&lt;/span&gt;
          &lt;span class=&quot;n&quot;&gt;linkBefore&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;(&lt;/span&gt;&lt;span class=&quot;n&quot;&gt;element&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;,&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;node&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;(&lt;/span&gt;&lt;span class=&quot;n&quot;&gt;index&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;));&lt;/span&gt;
      &lt;span class=&quot;o&quot;&gt;}&lt;/span&gt;
  &lt;span class=&quot;o&quot;&gt;}&lt;/span&gt;
  &lt;span class=&quot;c1&quot;&gt;//将一个集合中元素添加在指定位置之后，注意双向链表中指针值的设置&lt;/span&gt;
  &lt;span class=&quot;nd&quot;&gt;@Override&lt;/span&gt;
  &lt;span class=&quot;kd&quot;&gt;public&lt;/span&gt; &lt;span class=&quot;kt&quot;&gt;boolean&lt;/span&gt; &lt;span class=&quot;nf&quot;&gt;addAll&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;(&lt;/span&gt;&lt;span class=&quot;kt&quot;&gt;int&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;index&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;,&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;Collection&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;&amp;lt;?&lt;/span&gt; &lt;span class=&quot;kd&quot;&gt;extends&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;E&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;&amp;gt;&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;c&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;)&lt;/span&gt; &lt;span class=&quot;o&quot;&gt;{&lt;/span&gt;
      &lt;span class=&quot;c1&quot;&gt;//检验插入位置是否合法&lt;/span&gt;
      &lt;span class=&quot;n&quot;&gt;checkPositionIndex&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;(&lt;/span&gt;&lt;span class=&quot;n&quot;&gt;index&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;);&lt;/span&gt;

      &lt;span class=&quot;c1&quot;&gt;//将这个集合中的保存到新数组中，再进行操作，这是一种“安全”的做法&lt;/span&gt;
      &lt;span class=&quot;c1&quot;&gt;//使用toArray的目的是为了调用者可以自由的操作这个数组，而不会影响原来的集合&lt;/span&gt;
      &lt;span class=&quot;c1&quot;&gt;//返回的是对象数组，因为将集合类本身并不知道具体是什么类型，因此无法以最具体的类型声明数组&lt;/span&gt;
      &lt;span class=&quot;c1&quot;&gt;//调用此方法也意味着我们要进行强制类型转换，不过可以像addAll这样通过参数的类型参数来限制保证正确的类型&lt;/span&gt;
      &lt;span class=&quot;n&quot;&gt;Object&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;[]&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;a&lt;/span&gt; &lt;span class=&quot;o&quot;&gt;=&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;c&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;.&lt;/span&gt;&lt;span class=&quot;na&quot;&gt;toArray&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;();&lt;/span&gt;
      &lt;span class=&quot;kt&quot;&gt;int&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;numNew&lt;/span&gt; &lt;span class=&quot;o&quot;&gt;=&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;a&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;.&lt;/span&gt;&lt;span class=&quot;na&quot;&gt;length&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;;&lt;/span&gt; &lt;span class=&quot;c1&quot;&gt;//arraylength指令（乱入一记字节码指令）&lt;/span&gt;
      &lt;span class=&quot;k&quot;&gt;if&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;(&lt;/span&gt;&lt;span class=&quot;n&quot;&gt;numNew&lt;/span&gt; &lt;span class=&quot;o&quot;&gt;==&lt;/span&gt; &lt;span class=&quot;mi&quot;&gt;0&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;)&lt;/span&gt;
          &lt;span class=&quot;k&quot;&gt;return&lt;/span&gt; &lt;span class=&quot;kc&quot;&gt;false&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;;&lt;/span&gt;

      &lt;span class=&quot;c1&quot;&gt;//声明两个变量（指针）用来辅助设置插入过程中前后结点的指针值&lt;/span&gt;
      &lt;span class=&quot;c1&quot;&gt;//保存succ最后修改这个结点的prev指针（如果不为空的话）&lt;/span&gt;
      &lt;span class=&quot;n&quot;&gt;Node&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;&amp;lt;&lt;/span&gt;&lt;span class=&quot;n&quot;&gt;E&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;&amp;gt;&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;pred&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;,&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;succ&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;;&lt;/span&gt;
      &lt;span class=&quot;c1&quot;&gt;//插入位置正好是末尾，无法通过node()查找定位到&lt;/span&gt;
      &lt;span class=&quot;c1&quot;&gt;//否则找到index位置的结点，并确定pred的值&lt;/span&gt;
      &lt;span class=&quot;k&quot;&gt;if&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;(&lt;/span&gt;&lt;span class=&quot;n&quot;&gt;index&lt;/span&gt; &lt;span class=&quot;o&quot;&gt;==&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;size&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;)&lt;/span&gt; &lt;span class=&quot;o&quot;&gt;{&lt;/span&gt;
          &lt;span class=&quot;n&quot;&gt;pred&lt;/span&gt; &lt;span class=&quot;o&quot;&gt;=&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;last&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;;&lt;/span&gt;
          &lt;span class=&quot;n&quot;&gt;succ&lt;/span&gt; &lt;span class=&quot;o&quot;&gt;=&lt;/span&gt; &lt;span class=&quot;kc&quot;&gt;null&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;;&lt;/span&gt;
      &lt;span class=&quot;o&quot;&gt;}&lt;/span&gt; &lt;span class=&quot;k&quot;&gt;else&lt;/span&gt; &lt;span class=&quot;o&quot;&gt;{&lt;/span&gt;
          &lt;span class=&quot;n&quot;&gt;succ&lt;/span&gt; &lt;span class=&quot;o&quot;&gt;=&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;node&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;(&lt;/span&gt;&lt;span class=&quot;n&quot;&gt;index&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;);&lt;/span&gt;
          &lt;span class=&quot;n&quot;&gt;pred&lt;/span&gt; &lt;span class=&quot;o&quot;&gt;=&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;succ&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;.&lt;/span&gt;&lt;span class=&quot;na&quot;&gt;prev&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;;&lt;/span&gt;
      &lt;span class=&quot;o&quot;&gt;}&lt;/span&gt;

      &lt;span class=&quot;k&quot;&gt;for&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;(&lt;/span&gt;&lt;span class=&quot;n&quot;&gt;Object&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;o&lt;/span&gt; &lt;span class=&quot;o&quot;&gt;:&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;a&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;)&lt;/span&gt; &lt;span class=&quot;o&quot;&gt;{&lt;/span&gt;
          &lt;span class=&quot;nd&quot;&gt;@SuppressWarnings&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;(&lt;/span&gt;&lt;span class=&quot;s&quot;&gt;&quot;unchecked&quot;&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;)&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;E&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;element&lt;/span&gt; &lt;span class=&quot;o&quot;&gt;=&lt;/span&gt; &lt;span class=&quot;o&quot;&gt;(&lt;/span&gt;&lt;span class=&quot;n&quot;&gt;E&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;)&lt;/span&gt;&lt;span class=&quot;n&quot;&gt;o&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;;&lt;/span&gt;
          &lt;span class=&quot;n&quot;&gt;Node&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;&amp;lt;&lt;/span&gt;&lt;span class=&quot;n&quot;&gt;E&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;&amp;gt;&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;newNode&lt;/span&gt; &lt;span class=&quot;o&quot;&gt;=&lt;/span&gt; &lt;span class=&quot;k&quot;&gt;new&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;Node&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;&amp;lt;&amp;gt;(&lt;/span&gt;&lt;span class=&quot;n&quot;&gt;element&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;,&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;pred&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;,&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;succ&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;);&lt;/span&gt;
          &lt;span class=&quot;k&quot;&gt;if&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;(&lt;/span&gt;&lt;span class=&quot;n&quot;&gt;pred&lt;/span&gt; &lt;span class=&quot;o&quot;&gt;==&lt;/span&gt; &lt;span class=&quot;kc&quot;&gt;null&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;)&lt;/span&gt; &lt;span class=&quot;c1&quot;&gt;//在表头插入，设置frist值&lt;/span&gt;
              &lt;span class=&quot;n&quot;&gt;first&lt;/span&gt; &lt;span class=&quot;o&quot;&gt;=&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;newNode&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;;&lt;/span&gt;
          &lt;span class=&quot;k&quot;&gt;else&lt;/span&gt;
              &lt;span class=&quot;n&quot;&gt;pred&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;.&lt;/span&gt;&lt;span class=&quot;na&quot;&gt;next&lt;/span&gt; &lt;span class=&quot;o&quot;&gt;=&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;newNode&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;;&lt;/span&gt;
          &lt;span class=&quot;n&quot;&gt;pred&lt;/span&gt; &lt;span class=&quot;o&quot;&gt;=&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;newNode&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;;&lt;/span&gt;
      &lt;span class=&quot;o&quot;&gt;}&lt;/span&gt;

      &lt;span class=&quot;c1&quot;&gt;//设置后续结点的prev&lt;/span&gt;
      &lt;span class=&quot;k&quot;&gt;if&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;(&lt;/span&gt;&lt;span class=&quot;n&quot;&gt;succ&lt;/span&gt; &lt;span class=&quot;o&quot;&gt;==&lt;/span&gt; &lt;span class=&quot;kc&quot;&gt;null&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;)&lt;/span&gt; &lt;span class=&quot;c1&quot;&gt;//在末尾插入修改last的指向&lt;/span&gt;
          &lt;span class=&quot;n&quot;&gt;last&lt;/span&gt; &lt;span class=&quot;o&quot;&gt;=&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;pred&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;;&lt;/span&gt;
      &lt;span class=&quot;k&quot;&gt;else&lt;/span&gt; &lt;span class=&quot;o&quot;&gt;{&lt;/span&gt;
          &lt;span class=&quot;n&quot;&gt;pred&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;.&lt;/span&gt;&lt;span class=&quot;na&quot;&gt;next&lt;/span&gt; &lt;span class=&quot;o&quot;&gt;=&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;succ&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;;&lt;/span&gt;
          &lt;span class=&quot;n&quot;&gt;succ&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;.&lt;/span&gt;&lt;span class=&quot;na&quot;&gt;prev&lt;/span&gt; &lt;span class=&quot;o&quot;&gt;=&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;pred&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;;&lt;/span&gt;
      &lt;span class=&quot;o&quot;&gt;}&lt;/span&gt;

      &lt;span class=&quot;n&quot;&gt;size&lt;/span&gt; &lt;span class=&quot;o&quot;&gt;+=&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;numNew&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;;&lt;/span&gt;
      &lt;span class=&quot;o&quot;&gt;++&lt;/span&gt;&lt;span class=&quot;n&quot;&gt;modCount&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;;&lt;/span&gt;

      &lt;span class=&quot;k&quot;&gt;return&lt;/span&gt; &lt;span class=&quot;kc&quot;&gt;true&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;;&lt;/span&gt;
  &lt;span class=&quot;o&quot;&gt;}&lt;/span&gt;
  &lt;span class=&quot;nd&quot;&gt;@Override&lt;/span&gt;
  &lt;span class=&quot;kd&quot;&gt;public&lt;/span&gt; &lt;span class=&quot;kt&quot;&gt;boolean&lt;/span&gt; &lt;span class=&quot;nf&quot;&gt;addAll&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;(&lt;/span&gt;&lt;span class=&quot;n&quot;&gt;Collection&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;&amp;lt;?&lt;/span&gt; &lt;span class=&quot;kd&quot;&gt;extends&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;E&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;&amp;gt;&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;c&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;)&lt;/span&gt; &lt;span class=&quot;o&quot;&gt;{&lt;/span&gt;
      &lt;span class=&quot;n&quot;&gt;addAll&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;(&lt;/span&gt;&lt;span class=&quot;n&quot;&gt;size&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;,&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;c&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;);&lt;/span&gt;
      &lt;span class=&quot;k&quot;&gt;return&lt;/span&gt; &lt;span class=&quot;kc&quot;&gt;true&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;;&lt;/span&gt;
  &lt;span class=&quot;o&quot;&gt;}&lt;/span&gt;
  &lt;span class=&quot;nd&quot;&gt;@Override&lt;/span&gt;
  &lt;span class=&quot;kd&quot;&gt;public&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;E&lt;/span&gt; &lt;span class=&quot;nf&quot;&gt;get&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;(&lt;/span&gt;&lt;span class=&quot;kt&quot;&gt;int&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;index&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;)&lt;/span&gt; &lt;span class=&quot;o&quot;&gt;{&lt;/span&gt;
      &lt;span class=&quot;c1&quot;&gt;//检验索引值是否合法，不合法抛出异常&lt;/span&gt;
      &lt;span class=&quot;n&quot;&gt;checkElementIndex&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;(&lt;/span&gt;&lt;span class=&quot;n&quot;&gt;index&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;);&lt;/span&gt;
      &lt;span class=&quot;k&quot;&gt;return&lt;/span&gt; &lt;span class=&quot;nf&quot;&gt;node&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;(&lt;/span&gt;&lt;span class=&quot;n&quot;&gt;index&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;).&lt;/span&gt;&lt;span class=&quot;na&quot;&gt;item&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;;&lt;/span&gt;
  &lt;span class=&quot;o&quot;&gt;}&lt;/span&gt;
  &lt;span class=&quot;c1&quot;&gt;//设置并返回旧值&lt;/span&gt;
  &lt;span class=&quot;nd&quot;&gt;@Override&lt;/span&gt;
  &lt;span class=&quot;kd&quot;&gt;public&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;E&lt;/span&gt; &lt;span class=&quot;nf&quot;&gt;set&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;(&lt;/span&gt;&lt;span class=&quot;kt&quot;&gt;int&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;index&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;,&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;E&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;element&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;)&lt;/span&gt; &lt;span class=&quot;o&quot;&gt;{&lt;/span&gt;
      &lt;span class=&quot;c1&quot;&gt;//检验索引值是否合法，不合法抛出异常&lt;/span&gt;
      &lt;span class=&quot;n&quot;&gt;checkElementIndex&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;(&lt;/span&gt;&lt;span class=&quot;n&quot;&gt;index&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;);&lt;/span&gt;
      &lt;span class=&quot;n&quot;&gt;Node&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;&amp;lt;&lt;/span&gt;&lt;span class=&quot;n&quot;&gt;E&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;&amp;gt;&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;x&lt;/span&gt; &lt;span class=&quot;o&quot;&gt;=&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;node&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;(&lt;/span&gt;&lt;span class=&quot;n&quot;&gt;index&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;);&lt;/span&gt;
      &lt;span class=&quot;n&quot;&gt;E&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;oldVal&lt;/span&gt; &lt;span class=&quot;o&quot;&gt;=&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;x&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;.&lt;/span&gt;&lt;span class=&quot;na&quot;&gt;item&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;;&lt;/span&gt;
      &lt;span class=&quot;n&quot;&gt;x&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;.&lt;/span&gt;&lt;span class=&quot;na&quot;&gt;item&lt;/span&gt; &lt;span class=&quot;o&quot;&gt;=&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;element&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;;&lt;/span&gt;
      &lt;span class=&quot;k&quot;&gt;return&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;oldVal&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;;&lt;/span&gt;
  &lt;span class=&quot;o&quot;&gt;}&lt;/span&gt;
  &lt;span class=&quot;nd&quot;&gt;@Override&lt;/span&gt;
  &lt;span class=&quot;kd&quot;&gt;public&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;E&lt;/span&gt; &lt;span class=&quot;nf&quot;&gt;remove&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;(&lt;/span&gt;&lt;span class=&quot;kt&quot;&gt;int&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;index&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;)&lt;/span&gt; &lt;span class=&quot;o&quot;&gt;{&lt;/span&gt;
      &lt;span class=&quot;n&quot;&gt;checkElementIndex&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;(&lt;/span&gt;&lt;span class=&quot;n&quot;&gt;index&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;);&lt;/span&gt;
      &lt;span class=&quot;k&quot;&gt;return&lt;/span&gt; &lt;span class=&quot;nf&quot;&gt;unlink&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;(&lt;/span&gt;&lt;span class=&quot;n&quot;&gt;node&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;(&lt;/span&gt;&lt;span class=&quot;n&quot;&gt;index&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;));&lt;/span&gt;
  &lt;span class=&quot;o&quot;&gt;}&lt;/span&gt;
  &lt;span class=&quot;nd&quot;&gt;@Override&lt;/span&gt;
  &lt;span class=&quot;kd&quot;&gt;public&lt;/span&gt; &lt;span class=&quot;kt&quot;&gt;boolean&lt;/span&gt; &lt;span class=&quot;nf&quot;&gt;remove&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;(&lt;/span&gt;&lt;span class=&quot;n&quot;&gt;Object&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;o&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;)&lt;/span&gt; &lt;span class=&quot;o&quot;&gt;{&lt;/span&gt;
      &lt;span class=&quot;k&quot;&gt;if&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;(&lt;/span&gt;&lt;span class=&quot;n&quot;&gt;o&lt;/span&gt; &lt;span class=&quot;o&quot;&gt;==&lt;/span&gt; &lt;span class=&quot;kc&quot;&gt;null&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;)&lt;/span&gt; &lt;span class=&quot;o&quot;&gt;{&lt;/span&gt;
          &lt;span class=&quot;k&quot;&gt;for&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;(&lt;/span&gt;&lt;span class=&quot;n&quot;&gt;Node&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;&amp;lt;&lt;/span&gt;&lt;span class=&quot;n&quot;&gt;E&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;&amp;gt;&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;x&lt;/span&gt; &lt;span class=&quot;o&quot;&gt;=&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;first&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;;&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;x&lt;/span&gt; &lt;span class=&quot;o&quot;&gt;!=&lt;/span&gt; &lt;span class=&quot;kc&quot;&gt;null&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;;&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;x&lt;/span&gt; &lt;span class=&quot;o&quot;&gt;=&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;x&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;.&lt;/span&gt;&lt;span class=&quot;na&quot;&gt;next&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;)&lt;/span&gt; &lt;span class=&quot;o&quot;&gt;{&lt;/span&gt;
              &lt;span class=&quot;k&quot;&gt;if&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;(&lt;/span&gt;&lt;span class=&quot;n&quot;&gt;x&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;.&lt;/span&gt;&lt;span class=&quot;na&quot;&gt;item&lt;/span&gt; &lt;span class=&quot;o&quot;&gt;==&lt;/span&gt; &lt;span class=&quot;kc&quot;&gt;null&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;)&lt;/span&gt; &lt;span class=&quot;o&quot;&gt;{&lt;/span&gt;
                  &lt;span class=&quot;n&quot;&gt;unlink&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;(&lt;/span&gt;&lt;span class=&quot;n&quot;&gt;x&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;);&lt;/span&gt;
                  &lt;span class=&quot;k&quot;&gt;return&lt;/span&gt; &lt;span class=&quot;kc&quot;&gt;true&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;;&lt;/span&gt;
              &lt;span class=&quot;o&quot;&gt;}&lt;/span&gt;
          &lt;span class=&quot;o&quot;&gt;}&lt;/span&gt;
      &lt;span class=&quot;o&quot;&gt;}&lt;/span&gt; &lt;span class=&quot;k&quot;&gt;else&lt;/span&gt; &lt;span class=&quot;o&quot;&gt;{&lt;/span&gt;
          &lt;span class=&quot;k&quot;&gt;for&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;(&lt;/span&gt;&lt;span class=&quot;n&quot;&gt;Node&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;&amp;lt;&lt;/span&gt;&lt;span class=&quot;n&quot;&gt;E&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;&amp;gt;&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;x&lt;/span&gt; &lt;span class=&quot;o&quot;&gt;=&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;first&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;;&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;x&lt;/span&gt; &lt;span class=&quot;o&quot;&gt;!=&lt;/span&gt; &lt;span class=&quot;kc&quot;&gt;null&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;;&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;x&lt;/span&gt; &lt;span class=&quot;o&quot;&gt;=&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;x&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;.&lt;/span&gt;&lt;span class=&quot;na&quot;&gt;next&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;)&lt;/span&gt; &lt;span class=&quot;o&quot;&gt;{&lt;/span&gt;
              &lt;span class=&quot;k&quot;&gt;if&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;(&lt;/span&gt;&lt;span class=&quot;n&quot;&gt;o&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;.&lt;/span&gt;&lt;span class=&quot;na&quot;&gt;equals&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;(&lt;/span&gt;&lt;span class=&quot;n&quot;&gt;x&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;.&lt;/span&gt;&lt;span class=&quot;na&quot;&gt;item&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;))&lt;/span&gt; &lt;span class=&quot;o&quot;&gt;{&lt;/span&gt;
                  &lt;span class=&quot;n&quot;&gt;unlink&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;(&lt;/span&gt;&lt;span class=&quot;n&quot;&gt;x&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;);&lt;/span&gt;
                  &lt;span class=&quot;k&quot;&gt;return&lt;/span&gt; &lt;span class=&quot;kc&quot;&gt;true&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;;&lt;/span&gt;
              &lt;span class=&quot;o&quot;&gt;}&lt;/span&gt;
          &lt;span class=&quot;o&quot;&gt;}&lt;/span&gt;
      &lt;span class=&quot;o&quot;&gt;}&lt;/span&gt;
      &lt;span class=&quot;k&quot;&gt;return&lt;/span&gt; &lt;span class=&quot;kc&quot;&gt;false&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;;&lt;/span&gt;
  &lt;span class=&quot;o&quot;&gt;}&lt;/span&gt;
  &lt;span class=&quot;c1&quot;&gt;//清空链表，尤其注意置空，让结点之间，结点和元素之间不在互相引用的存在堆中，让它们“独立”的接受垃圾回收&lt;/span&gt;
  &lt;span class=&quot;nd&quot;&gt;@Override&lt;/span&gt;
  &lt;span class=&quot;kd&quot;&gt;public&lt;/span&gt; &lt;span class=&quot;kt&quot;&gt;void&lt;/span&gt; &lt;span class=&quot;nf&quot;&gt;clear&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;()&lt;/span&gt; &lt;span class=&quot;o&quot;&gt;{&lt;/span&gt;
      &lt;span class=&quot;k&quot;&gt;for&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;(&lt;/span&gt;&lt;span class=&quot;n&quot;&gt;Node&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;&amp;lt;&lt;/span&gt;&lt;span class=&quot;n&quot;&gt;E&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;&amp;gt;&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;x&lt;/span&gt; &lt;span class=&quot;o&quot;&gt;=&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;first&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;;&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;x&lt;/span&gt; &lt;span class=&quot;o&quot;&gt;!=&lt;/span&gt; &lt;span class=&quot;kc&quot;&gt;null&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;;)&lt;/span&gt; &lt;span class=&quot;o&quot;&gt;{&lt;/span&gt;
          &lt;span class=&quot;n&quot;&gt;Node&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;&amp;lt;&lt;/span&gt;&lt;span class=&quot;n&quot;&gt;E&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;&amp;gt;&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;next&lt;/span&gt; &lt;span class=&quot;o&quot;&gt;=&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;x&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;.&lt;/span&gt;&lt;span class=&quot;na&quot;&gt;next&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;;&lt;/span&gt;
          &lt;span class=&quot;c1&quot;&gt;//置空，不要影响原来被引用对象的垃圾回收&lt;/span&gt;
          &lt;span class=&quot;n&quot;&gt;x&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;.&lt;/span&gt;&lt;span class=&quot;na&quot;&gt;item&lt;/span&gt; &lt;span class=&quot;o&quot;&gt;=&lt;/span&gt; &lt;span class=&quot;kc&quot;&gt;null&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;;&lt;/span&gt;
          &lt;span class=&quot;n&quot;&gt;x&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;.&lt;/span&gt;&lt;span class=&quot;na&quot;&gt;next&lt;/span&gt; &lt;span class=&quot;o&quot;&gt;=&lt;/span&gt; &lt;span class=&quot;kc&quot;&gt;null&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;;&lt;/span&gt;
          &lt;span class=&quot;n&quot;&gt;x&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;.&lt;/span&gt;&lt;span class=&quot;na&quot;&gt;prev&lt;/span&gt; &lt;span class=&quot;o&quot;&gt;=&lt;/span&gt; &lt;span class=&quot;kc&quot;&gt;null&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;;&lt;/span&gt;
          &lt;span class=&quot;n&quot;&gt;x&lt;/span&gt; &lt;span class=&quot;o&quot;&gt;=&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;next&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;;&lt;/span&gt;
      &lt;span class=&quot;o&quot;&gt;}&lt;/span&gt;
      &lt;span class=&quot;n&quot;&gt;first&lt;/span&gt; &lt;span class=&quot;o&quot;&gt;=&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;last&lt;/span&gt; &lt;span class=&quot;o&quot;&gt;=&lt;/span&gt; &lt;span class=&quot;kc&quot;&gt;null&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;;&lt;/span&gt;
      &lt;span class=&quot;n&quot;&gt;size&lt;/span&gt; &lt;span class=&quot;o&quot;&gt;=&lt;/span&gt; &lt;span class=&quot;mi&quot;&gt;0&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;;&lt;/span&gt;
      &lt;span class=&quot;o&quot;&gt;++&lt;/span&gt;&lt;span class=&quot;n&quot;&gt;modCount&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;;&lt;/span&gt;
  &lt;span class=&quot;o&quot;&gt;}&lt;/span&gt;
  &lt;span class=&quot;c1&quot;&gt;//查找指定对象第一次出现的位置&lt;/span&gt;
  &lt;span class=&quot;nd&quot;&gt;@Override&lt;/span&gt;
  &lt;span class=&quot;kd&quot;&gt;public&lt;/span&gt; &lt;span class=&quot;kt&quot;&gt;int&lt;/span&gt; &lt;span class=&quot;nf&quot;&gt;indexOf&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;(&lt;/span&gt;&lt;span class=&quot;n&quot;&gt;Object&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;o&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;)&lt;/span&gt; &lt;span class=&quot;o&quot;&gt;{&lt;/span&gt;
      &lt;span class=&quot;kt&quot;&gt;int&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;index&lt;/span&gt; &lt;span class=&quot;o&quot;&gt;=&lt;/span&gt; &lt;span class=&quot;mi&quot;&gt;0&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;;&lt;/span&gt;
      &lt;span class=&quot;k&quot;&gt;if&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;(&lt;/span&gt;&lt;span class=&quot;n&quot;&gt;o&lt;/span&gt; &lt;span class=&quot;o&quot;&gt;==&lt;/span&gt; &lt;span class=&quot;kc&quot;&gt;null&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;)&lt;/span&gt; &lt;span class=&quot;o&quot;&gt;{&lt;/span&gt;
          &lt;span class=&quot;k&quot;&gt;for&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;(&lt;/span&gt;&lt;span class=&quot;n&quot;&gt;Node&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;&amp;lt;&lt;/span&gt;&lt;span class=&quot;n&quot;&gt;E&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;&amp;gt;&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;x&lt;/span&gt; &lt;span class=&quot;o&quot;&gt;=&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;first&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;;&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;x&lt;/span&gt; &lt;span class=&quot;o&quot;&gt;!=&lt;/span&gt; &lt;span class=&quot;kc&quot;&gt;null&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;;&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;x&lt;/span&gt; &lt;span class=&quot;o&quot;&gt;=&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;x&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;.&lt;/span&gt;&lt;span class=&quot;na&quot;&gt;next&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;)&lt;/span&gt; &lt;span class=&quot;o&quot;&gt;{&lt;/span&gt;
              &lt;span class=&quot;k&quot;&gt;if&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;(&lt;/span&gt;&lt;span class=&quot;n&quot;&gt;x&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;.&lt;/span&gt;&lt;span class=&quot;na&quot;&gt;item&lt;/span&gt; &lt;span class=&quot;o&quot;&gt;==&lt;/span&gt; &lt;span class=&quot;kc&quot;&gt;null&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;)&lt;/span&gt;
                  &lt;span class=&quot;k&quot;&gt;return&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;index&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;;&lt;/span&gt;
              &lt;span class=&quot;n&quot;&gt;index&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;++;&lt;/span&gt;
          &lt;span class=&quot;o&quot;&gt;}&lt;/span&gt;
      &lt;span class=&quot;o&quot;&gt;}&lt;/span&gt; &lt;span class=&quot;k&quot;&gt;else&lt;/span&gt; &lt;span class=&quot;o&quot;&gt;{&lt;/span&gt;
          &lt;span class=&quot;k&quot;&gt;for&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;(&lt;/span&gt;&lt;span class=&quot;n&quot;&gt;Node&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;&amp;lt;&lt;/span&gt;&lt;span class=&quot;n&quot;&gt;E&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;&amp;gt;&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;x&lt;/span&gt; &lt;span class=&quot;o&quot;&gt;=&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;first&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;;&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;x&lt;/span&gt; &lt;span class=&quot;o&quot;&gt;!=&lt;/span&gt; &lt;span class=&quot;kc&quot;&gt;null&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;;&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;x&lt;/span&gt; &lt;span class=&quot;o&quot;&gt;=&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;x&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;.&lt;/span&gt;&lt;span class=&quot;na&quot;&gt;next&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;)&lt;/span&gt; &lt;span class=&quot;o&quot;&gt;{&lt;/span&gt;
              &lt;span class=&quot;k&quot;&gt;if&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;(&lt;/span&gt;&lt;span class=&quot;n&quot;&gt;o&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;.&lt;/span&gt;&lt;span class=&quot;na&quot;&gt;equals&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;(&lt;/span&gt;&lt;span class=&quot;n&quot;&gt;x&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;.&lt;/span&gt;&lt;span class=&quot;na&quot;&gt;item&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;))&lt;/span&gt;
                  &lt;span class=&quot;k&quot;&gt;return&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;index&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;;&lt;/span&gt;
              &lt;span class=&quot;n&quot;&gt;index&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;++;&lt;/span&gt;
          &lt;span class=&quot;o&quot;&gt;}&lt;/span&gt;
      &lt;span class=&quot;o&quot;&gt;}&lt;/span&gt;
      &lt;span class=&quot;k&quot;&gt;return&lt;/span&gt; &lt;span class=&quot;o&quot;&gt;-&lt;/span&gt;&lt;span class=&quot;mi&quot;&gt;1&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;;&lt;/span&gt;
  &lt;span class=&quot;o&quot;&gt;}&lt;/span&gt;
  &lt;span class=&quot;c1&quot;&gt;//查找指定对象最后一次出现的位置&lt;/span&gt;
  &lt;span class=&quot;nd&quot;&gt;@Override&lt;/span&gt;
  &lt;span class=&quot;kd&quot;&gt;public&lt;/span&gt; &lt;span class=&quot;kt&quot;&gt;int&lt;/span&gt; &lt;span class=&quot;nf&quot;&gt;lastIndexOf&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;(&lt;/span&gt;&lt;span class=&quot;n&quot;&gt;Object&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;o&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;)&lt;/span&gt; &lt;span class=&quot;o&quot;&gt;{&lt;/span&gt;
      &lt;span class=&quot;kt&quot;&gt;int&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;index&lt;/span&gt; &lt;span class=&quot;o&quot;&gt;=&lt;/span&gt; &lt;span class=&quot;mi&quot;&gt;0&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;;&lt;/span&gt;

      &lt;span class=&quot;k&quot;&gt;if&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;(&lt;/span&gt;&lt;span class=&quot;n&quot;&gt;o&lt;/span&gt; &lt;span class=&quot;o&quot;&gt;==&lt;/span&gt; &lt;span class=&quot;kc&quot;&gt;null&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;)&lt;/span&gt; &lt;span class=&quot;o&quot;&gt;{&lt;/span&gt;
          &lt;span class=&quot;k&quot;&gt;for&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;(&lt;/span&gt;&lt;span class=&quot;n&quot;&gt;Node&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;&amp;lt;&lt;/span&gt;&lt;span class=&quot;n&quot;&gt;E&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;&amp;gt;&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;x&lt;/span&gt; &lt;span class=&quot;o&quot;&gt;=&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;last&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;;&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;x&lt;/span&gt; &lt;span class=&quot;o&quot;&gt;!=&lt;/span&gt; &lt;span class=&quot;kc&quot;&gt;null&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;;&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;x&lt;/span&gt; &lt;span class=&quot;o&quot;&gt;=&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;x&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;.&lt;/span&gt;&lt;span class=&quot;na&quot;&gt;prev&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;)&lt;/span&gt; &lt;span class=&quot;o&quot;&gt;{&lt;/span&gt;
              &lt;span class=&quot;k&quot;&gt;if&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;(&lt;/span&gt;&lt;span class=&quot;n&quot;&gt;x&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;.&lt;/span&gt;&lt;span class=&quot;na&quot;&gt;item&lt;/span&gt; &lt;span class=&quot;o&quot;&gt;==&lt;/span&gt; &lt;span class=&quot;kc&quot;&gt;null&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;)&lt;/span&gt;
                  &lt;span class=&quot;k&quot;&gt;return&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;index&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;;&lt;/span&gt;
              &lt;span class=&quot;n&quot;&gt;index&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;++;&lt;/span&gt;
          &lt;span class=&quot;o&quot;&gt;}&lt;/span&gt;
      &lt;span class=&quot;o&quot;&gt;}&lt;/span&gt; &lt;span class=&quot;k&quot;&gt;else&lt;/span&gt; &lt;span class=&quot;o&quot;&gt;{&lt;/span&gt;
          &lt;span class=&quot;k&quot;&gt;for&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;(&lt;/span&gt;&lt;span class=&quot;n&quot;&gt;Node&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;&amp;lt;&lt;/span&gt;&lt;span class=&quot;n&quot;&gt;E&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;&amp;gt;&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;x&lt;/span&gt; &lt;span class=&quot;o&quot;&gt;=&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;last&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;;&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;x&lt;/span&gt; &lt;span class=&quot;o&quot;&gt;!=&lt;/span&gt; &lt;span class=&quot;kc&quot;&gt;null&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;;&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;x&lt;/span&gt; &lt;span class=&quot;o&quot;&gt;=&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;x&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;.&lt;/span&gt;&lt;span class=&quot;na&quot;&gt;prev&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;)&lt;/span&gt; &lt;span class=&quot;o&quot;&gt;{&lt;/span&gt;
              &lt;span class=&quot;k&quot;&gt;if&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;(&lt;/span&gt;&lt;span class=&quot;n&quot;&gt;o&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;.&lt;/span&gt;&lt;span class=&quot;na&quot;&gt;equals&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;(&lt;/span&gt;&lt;span class=&quot;n&quot;&gt;x&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;.&lt;/span&gt;&lt;span class=&quot;na&quot;&gt;item&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;))&lt;/span&gt;
                  &lt;span class=&quot;k&quot;&gt;return&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;index&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;;&lt;/span&gt;
              &lt;span class=&quot;n&quot;&gt;index&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;++;&lt;/span&gt;
          &lt;span class=&quot;o&quot;&gt;}&lt;/span&gt;
      &lt;span class=&quot;o&quot;&gt;}&lt;/span&gt;

      &lt;span class=&quot;k&quot;&gt;return&lt;/span&gt; &lt;span class=&quot;o&quot;&gt;-&lt;/span&gt;&lt;span class=&quot;mi&quot;&gt;1&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;;&lt;/span&gt;
  &lt;span class=&quot;o&quot;&gt;}&lt;/span&gt;
  &lt;span class=&quot;nd&quot;&gt;@Override&lt;/span&gt;
  &lt;span class=&quot;kd&quot;&gt;public&lt;/span&gt; &lt;span class=&quot;kt&quot;&gt;int&lt;/span&gt; &lt;span class=&quot;nf&quot;&gt;size&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;()&lt;/span&gt; &lt;span class=&quot;o&quot;&gt;{&lt;/span&gt;
      &lt;span class=&quot;k&quot;&gt;return&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;size&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;;&lt;/span&gt;
  &lt;span class=&quot;o&quot;&gt;}&lt;/span&gt;
  &lt;span class=&quot;c1&quot;&gt;//注意contains，indexOf，lastIndexOf方法接受的都是Object&lt;/span&gt;
  &lt;span class=&quot;nd&quot;&gt;@Override&lt;/span&gt;
  &lt;span class=&quot;kd&quot;&gt;public&lt;/span&gt; &lt;span class=&quot;kt&quot;&gt;boolean&lt;/span&gt; &lt;span class=&quot;nf&quot;&gt;contains&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;(&lt;/span&gt;&lt;span class=&quot;n&quot;&gt;Object&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;o&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;)&lt;/span&gt; &lt;span class=&quot;o&quot;&gt;{&lt;/span&gt;
      &lt;span class=&quot;k&quot;&gt;return&lt;/span&gt; &lt;span class=&quot;nf&quot;&gt;indexOf&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;(&lt;/span&gt;&lt;span class=&quot;n&quot;&gt;o&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;)&lt;/span&gt; &lt;span class=&quot;o&quot;&gt;!=&lt;/span&gt; &lt;span class=&quot;o&quot;&gt;-&lt;/span&gt;&lt;span class=&quot;mi&quot;&gt;1&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;;&lt;/span&gt;
  &lt;span class=&quot;o&quot;&gt;}&lt;/span&gt;
  &lt;span class=&quot;c1&quot;&gt;//列表迭代器&lt;/span&gt;
  &lt;span class=&quot;nd&quot;&gt;@Override&lt;/span&gt;
  &lt;span class=&quot;kd&quot;&gt;public&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;ListIterator&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;&amp;lt;&lt;/span&gt;&lt;span class=&quot;n&quot;&gt;E&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;&amp;gt;&lt;/span&gt; &lt;span class=&quot;nf&quot;&gt;listIterator&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;(&lt;/span&gt;&lt;span class=&quot;kt&quot;&gt;int&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;index&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;)&lt;/span&gt; &lt;span class=&quot;o&quot;&gt;{&lt;/span&gt;
      &lt;span class=&quot;n&quot;&gt;checkPositionIndex&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;(&lt;/span&gt;&lt;span class=&quot;n&quot;&gt;index&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;);&lt;/span&gt;
      &lt;span class=&quot;k&quot;&gt;return&lt;/span&gt; &lt;span class=&quot;k&quot;&gt;new&lt;/span&gt; &lt;span class=&quot;nf&quot;&gt;ListItr&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;(&lt;/span&gt;&lt;span class=&quot;n&quot;&gt;index&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;);&lt;/span&gt;
  &lt;span class=&quot;o&quot;&gt;}&lt;/span&gt;
  &lt;span class=&quot;c1&quot;&gt;//保存为数组，这里只能返回Object，因为不能通过泛型参数创建对象/数组对象&lt;/span&gt;
  &lt;span class=&quot;c1&quot;&gt;//通过toArray方法可以自由操作该集合内元素而不影响该集合&lt;/span&gt;
  &lt;span class=&quot;nd&quot;&gt;@Override&lt;/span&gt;
  &lt;span class=&quot;kd&quot;&gt;public&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;Object&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;[]&lt;/span&gt; &lt;span class=&quot;nf&quot;&gt;toArray&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;()&lt;/span&gt; &lt;span class=&quot;o&quot;&gt;{&lt;/span&gt;
      &lt;span class=&quot;n&quot;&gt;Object&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;[]&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;result&lt;/span&gt; &lt;span class=&quot;o&quot;&gt;=&lt;/span&gt; &lt;span class=&quot;k&quot;&gt;new&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;Object&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;[&lt;/span&gt;&lt;span class=&quot;n&quot;&gt;size&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;];&lt;/span&gt;
      &lt;span class=&quot;kt&quot;&gt;int&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;i&lt;/span&gt; &lt;span class=&quot;o&quot;&gt;=&lt;/span&gt; &lt;span class=&quot;mi&quot;&gt;0&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;;&lt;/span&gt;
      &lt;span class=&quot;k&quot;&gt;for&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;(&lt;/span&gt;&lt;span class=&quot;n&quot;&gt;Node&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;&amp;lt;&lt;/span&gt;&lt;span class=&quot;n&quot;&gt;E&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;&amp;gt;&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;x&lt;/span&gt; &lt;span class=&quot;o&quot;&gt;=&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;first&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;;&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;x&lt;/span&gt; &lt;span class=&quot;o&quot;&gt;!=&lt;/span&gt; &lt;span class=&quot;kc&quot;&gt;null&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;;&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;x&lt;/span&gt; &lt;span class=&quot;o&quot;&gt;=&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;x&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;.&lt;/span&gt;&lt;span class=&quot;na&quot;&gt;next&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;)&lt;/span&gt; &lt;span class=&quot;o&quot;&gt;{&lt;/span&gt;
          &lt;span class=&quot;n&quot;&gt;result&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;[&lt;/span&gt;&lt;span class=&quot;n&quot;&gt;i&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;++]&lt;/span&gt; &lt;span class=&quot;o&quot;&gt;=&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;x&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;.&lt;/span&gt;&lt;span class=&quot;na&quot;&gt;item&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;;&lt;/span&gt;
      &lt;span class=&quot;o&quot;&gt;}&lt;/span&gt;
      &lt;span class=&quot;k&quot;&gt;return&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;result&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;;&lt;/span&gt;
  &lt;span class=&quot;o&quot;&gt;}&lt;/span&gt;
  &lt;span class=&quot;c1&quot;&gt;//toArray的泛型方法版本，相对于toArray()来说可以进行必要的类型检查，但是创建数组的责任交给了调用者&lt;/span&gt;
  &lt;span class=&quot;nd&quot;&gt;@SuppressWarnings&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;(&lt;/span&gt;&lt;span class=&quot;s&quot;&gt;&quot;unchecked&quot;&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;)&lt;/span&gt;
  &lt;span class=&quot;nd&quot;&gt;@Override&lt;/span&gt;
  &lt;span class=&quot;kd&quot;&gt;public&lt;/span&gt; &lt;span class=&quot;o&quot;&gt;&amp;lt;&lt;/span&gt;&lt;span class=&quot;n&quot;&gt;T&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;&amp;gt;&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;T&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;[]&lt;/span&gt; &lt;span class=&quot;nf&quot;&gt;toArray&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;(&lt;/span&gt;&lt;span class=&quot;n&quot;&gt;T&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;[]&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;a&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;)&lt;/span&gt; &lt;span class=&quot;o&quot;&gt;{&lt;/span&gt;
      &lt;span class=&quot;c1&quot;&gt;//检查长度是否能够存放所有元素&lt;/span&gt;
      &lt;span class=&quot;k&quot;&gt;if&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;(&lt;/span&gt;&lt;span class=&quot;n&quot;&gt;a&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;.&lt;/span&gt;&lt;span class=&quot;na&quot;&gt;length&lt;/span&gt; &lt;span class=&quot;o&quot;&gt;&amp;lt;&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;size&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;)&lt;/span&gt; &lt;span class=&quot;c1&quot;&gt;//小于size重新通过反射创建&lt;/span&gt;
          &lt;span class=&quot;n&quot;&gt;a&lt;/span&gt; &lt;span class=&quot;o&quot;&gt;=&lt;/span&gt; &lt;span class=&quot;o&quot;&gt;(&lt;/span&gt;&lt;span class=&quot;n&quot;&gt;T&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;[])&lt;/span&gt;&lt;span class=&quot;n&quot;&gt;java&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;.&lt;/span&gt;&lt;span class=&quot;na&quot;&gt;lang&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;.&lt;/span&gt;&lt;span class=&quot;na&quot;&gt;reflect&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;.&lt;/span&gt;&lt;span class=&quot;na&quot;&gt;Array&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;.&lt;/span&gt;&lt;span class=&quot;na&quot;&gt;newInstance&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;(&lt;/span&gt;
                  &lt;span class=&quot;n&quot;&gt;a&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;.&lt;/span&gt;&lt;span class=&quot;na&quot;&gt;getClass&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;().&lt;/span&gt;&lt;span class=&quot;na&quot;&gt;getComponentType&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;(),&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;size&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;);&lt;/span&gt;

      &lt;span class=&quot;kt&quot;&gt;int&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;i&lt;/span&gt; &lt;span class=&quot;o&quot;&gt;=&lt;/span&gt; &lt;span class=&quot;mi&quot;&gt;0&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;;&lt;/span&gt;
      &lt;span class=&quot;c1&quot;&gt;//通过Object数组引用，可以避开泛型参数的限制，数组对象本身可以检查存入的类型是否正确，不正确保存ArrayStoreException&lt;/span&gt;
      &lt;span class=&quot;n&quot;&gt;Object&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;[]&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;result&lt;/span&gt; &lt;span class=&quot;o&quot;&gt;=&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;a&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;;&lt;/span&gt;
      &lt;span class=&quot;k&quot;&gt;for&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;(&lt;/span&gt;&lt;span class=&quot;n&quot;&gt;Node&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;&amp;lt;&lt;/span&gt;&lt;span class=&quot;n&quot;&gt;E&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;&amp;gt;&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;x&lt;/span&gt; &lt;span class=&quot;o&quot;&gt;=&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;first&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;;&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;x&lt;/span&gt; &lt;span class=&quot;o&quot;&gt;!=&lt;/span&gt; &lt;span class=&quot;kc&quot;&gt;null&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;;&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;x&lt;/span&gt; &lt;span class=&quot;o&quot;&gt;=&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;x&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;.&lt;/span&gt;&lt;span class=&quot;na&quot;&gt;next&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;)&lt;/span&gt; &lt;span class=&quot;o&quot;&gt;{&lt;/span&gt;
          &lt;span class=&quot;n&quot;&gt;result&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;[&lt;/span&gt;&lt;span class=&quot;n&quot;&gt;i&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;++]&lt;/span&gt; &lt;span class=&quot;o&quot;&gt;=&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;x&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;.&lt;/span&gt;&lt;span class=&quot;na&quot;&gt;item&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;;&lt;/span&gt;
      &lt;span class=&quot;o&quot;&gt;}&lt;/span&gt;

      &lt;span class=&quot;c1&quot;&gt;//如果数组长度大于集合长度，size位置置空&lt;/span&gt;
      &lt;span class=&quot;k&quot;&gt;if&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;(&lt;/span&gt;&lt;span class=&quot;n&quot;&gt;a&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;.&lt;/span&gt;&lt;span class=&quot;na&quot;&gt;length&lt;/span&gt; &lt;span class=&quot;o&quot;&gt;&amp;gt;&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;size&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;)&lt;/span&gt; &lt;span class=&quot;o&quot;&gt;{&lt;/span&gt;
          &lt;span class=&quot;n&quot;&gt;a&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;[&lt;/span&gt;&lt;span class=&quot;n&quot;&gt;size&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;]&lt;/span&gt; &lt;span class=&quot;o&quot;&gt;=&lt;/span&gt; &lt;span class=&quot;kc&quot;&gt;null&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;;&lt;/span&gt;
      &lt;span class=&quot;o&quot;&gt;}&lt;/span&gt;

      &lt;span class=&quot;k&quot;&gt;return&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;a&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;;&lt;/span&gt;
  &lt;span class=&quot;o&quot;&gt;}&lt;/span&gt;
&lt;/code&gt;&lt;/pre&gt;
        &lt;/div&gt;
      &lt;/li&gt;
    &lt;/ul&gt;
  &lt;/li&gt;
  &lt;li&gt;3-4 Deque双端队列的实现
    &lt;ul&gt;
      &lt;li&gt;3-4-1 与其他队列实现一样：offer（入队），poll（出队），peek（队首元素）不抛出异常，remove～（不同位置的删除方法），element（队首元素）为空是抛出异常；&lt;/li&gt;
      &lt;li&gt;3-4-2 现pop和push，栈操作，以链表头作为栈顶；
        &lt;div class=&quot;language-java highlighter-rouge&quot;&gt;&lt;pre class=&quot;highlight&quot;&gt;&lt;code&gt;    &lt;span class=&quot;nd&quot;&gt;@Override&lt;/span&gt;
    &lt;span class=&quot;kd&quot;&gt;public&lt;/span&gt; &lt;span class=&quot;kt&quot;&gt;void&lt;/span&gt; &lt;span class=&quot;nf&quot;&gt;addFirst&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;(&lt;/span&gt;&lt;span class=&quot;n&quot;&gt;E&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;e&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;)&lt;/span&gt; &lt;span class=&quot;o&quot;&gt;{&lt;/span&gt;
        &lt;span class=&quot;n&quot;&gt;linkFirst&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;(&lt;/span&gt;&lt;span class=&quot;n&quot;&gt;e&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;);&lt;/span&gt;
    &lt;span class=&quot;o&quot;&gt;}&lt;/span&gt;

    &lt;span class=&quot;nd&quot;&gt;@Override&lt;/span&gt;
    &lt;span class=&quot;kd&quot;&gt;public&lt;/span&gt; &lt;span class=&quot;kt&quot;&gt;void&lt;/span&gt; &lt;span class=&quot;nf&quot;&gt;addLast&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;(&lt;/span&gt;&lt;span class=&quot;n&quot;&gt;E&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;e&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;)&lt;/span&gt; &lt;span class=&quot;o&quot;&gt;{&lt;/span&gt;
        &lt;span class=&quot;n&quot;&gt;linkLast&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;(&lt;/span&gt;&lt;span class=&quot;n&quot;&gt;e&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;);&lt;/span&gt;
    &lt;span class=&quot;o&quot;&gt;}&lt;/span&gt;

    &lt;span class=&quot;nd&quot;&gt;@Override&lt;/span&gt;
    &lt;span class=&quot;kd&quot;&gt;public&lt;/span&gt; &lt;span class=&quot;kt&quot;&gt;boolean&lt;/span&gt; &lt;span class=&quot;nf&quot;&gt;offerFirst&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;(&lt;/span&gt;&lt;span class=&quot;n&quot;&gt;E&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;e&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;)&lt;/span&gt; &lt;span class=&quot;o&quot;&gt;{&lt;/span&gt;
        &lt;span class=&quot;n&quot;&gt;addFirst&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;(&lt;/span&gt;&lt;span class=&quot;n&quot;&gt;e&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;);&lt;/span&gt;
        &lt;span class=&quot;k&quot;&gt;return&lt;/span&gt; &lt;span class=&quot;kc&quot;&gt;true&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;;&lt;/span&gt;
    &lt;span class=&quot;o&quot;&gt;}&lt;/span&gt;

    &lt;span class=&quot;nd&quot;&gt;@Override&lt;/span&gt;
    &lt;span class=&quot;kd&quot;&gt;public&lt;/span&gt; &lt;span class=&quot;kt&quot;&gt;boolean&lt;/span&gt; &lt;span class=&quot;nf&quot;&gt;offerLast&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;(&lt;/span&gt;&lt;span class=&quot;n&quot;&gt;E&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;e&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;)&lt;/span&gt; &lt;span class=&quot;o&quot;&gt;{&lt;/span&gt;
        &lt;span class=&quot;n&quot;&gt;addLast&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;(&lt;/span&gt;&lt;span class=&quot;n&quot;&gt;e&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;);&lt;/span&gt;
        &lt;span class=&quot;k&quot;&gt;return&lt;/span&gt; &lt;span class=&quot;kc&quot;&gt;true&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;;&lt;/span&gt;
    &lt;span class=&quot;o&quot;&gt;}&lt;/span&gt;

    &lt;span class=&quot;nd&quot;&gt;@Override&lt;/span&gt;
    &lt;span class=&quot;kd&quot;&gt;public&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;E&lt;/span&gt; &lt;span class=&quot;nf&quot;&gt;removeFirst&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;()&lt;/span&gt; &lt;span class=&quot;o&quot;&gt;{&lt;/span&gt;
        &lt;span class=&quot;kd&quot;&gt;final&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;Node&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;&amp;lt;&lt;/span&gt;&lt;span class=&quot;n&quot;&gt;E&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;&amp;gt;&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;f&lt;/span&gt; &lt;span class=&quot;o&quot;&gt;=&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;first&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;;&lt;/span&gt;
        &lt;span class=&quot;k&quot;&gt;if&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;(&lt;/span&gt;&lt;span class=&quot;n&quot;&gt;f&lt;/span&gt; &lt;span class=&quot;o&quot;&gt;==&lt;/span&gt; &lt;span class=&quot;kc&quot;&gt;null&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;)&lt;/span&gt;
            &lt;span class=&quot;k&quot;&gt;throw&lt;/span&gt; &lt;span class=&quot;k&quot;&gt;new&lt;/span&gt; &lt;span class=&quot;nf&quot;&gt;NoSuchElementException&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;(&lt;/span&gt;&lt;span class=&quot;s&quot;&gt;&quot;first is not exist.&quot;&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;);&lt;/span&gt;
        &lt;span class=&quot;k&quot;&gt;return&lt;/span&gt; &lt;span class=&quot;nf&quot;&gt;unlinkFirst&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;(&lt;/span&gt;&lt;span class=&quot;n&quot;&gt;f&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;);&lt;/span&gt;
    &lt;span class=&quot;o&quot;&gt;}&lt;/span&gt;

    &lt;span class=&quot;nd&quot;&gt;@Override&lt;/span&gt;
    &lt;span class=&quot;kd&quot;&gt;public&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;E&lt;/span&gt; &lt;span class=&quot;nf&quot;&gt;removeLast&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;()&lt;/span&gt; &lt;span class=&quot;o&quot;&gt;{&lt;/span&gt;
        &lt;span class=&quot;kd&quot;&gt;final&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;Node&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;&amp;lt;&lt;/span&gt;&lt;span class=&quot;n&quot;&gt;E&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;&amp;gt;&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;l&lt;/span&gt; &lt;span class=&quot;o&quot;&gt;=&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;last&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;;&lt;/span&gt;
        &lt;span class=&quot;k&quot;&gt;if&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;(&lt;/span&gt;&lt;span class=&quot;n&quot;&gt;l&lt;/span&gt; &lt;span class=&quot;o&quot;&gt;==&lt;/span&gt; &lt;span class=&quot;kc&quot;&gt;null&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;)&lt;/span&gt;
            &lt;span class=&quot;k&quot;&gt;throw&lt;/span&gt; &lt;span class=&quot;k&quot;&gt;new&lt;/span&gt; &lt;span class=&quot;nf&quot;&gt;NoSuchElementException&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;(&lt;/span&gt;&lt;span class=&quot;s&quot;&gt;&quot;last is not exist.&quot;&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;);&lt;/span&gt;
        &lt;span class=&quot;k&quot;&gt;return&lt;/span&gt; &lt;span class=&quot;nf&quot;&gt;unlinkLast&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;(&lt;/span&gt;&lt;span class=&quot;n&quot;&gt;l&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;);&lt;/span&gt;
    &lt;span class=&quot;o&quot;&gt;}&lt;/span&gt;

    &lt;span class=&quot;c1&quot;&gt;//poll~方法不抛出异常，为空时返回null&lt;/span&gt;
    &lt;span class=&quot;nd&quot;&gt;@Override&lt;/span&gt;
    &lt;span class=&quot;kd&quot;&gt;public&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;E&lt;/span&gt; &lt;span class=&quot;nf&quot;&gt;pollFirst&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;()&lt;/span&gt; &lt;span class=&quot;o&quot;&gt;{&lt;/span&gt;
        &lt;span class=&quot;kd&quot;&gt;final&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;Node&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;&amp;lt;&lt;/span&gt;&lt;span class=&quot;n&quot;&gt;E&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;&amp;gt;&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;f&lt;/span&gt; &lt;span class=&quot;o&quot;&gt;=&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;first&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;;&lt;/span&gt;
        &lt;span class=&quot;k&quot;&gt;return&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;f&lt;/span&gt; &lt;span class=&quot;o&quot;&gt;==&lt;/span&gt; &lt;span class=&quot;kc&quot;&gt;null&lt;/span&gt; &lt;span class=&quot;o&quot;&gt;?&lt;/span&gt; &lt;span class=&quot;kc&quot;&gt;null&lt;/span&gt; &lt;span class=&quot;o&quot;&gt;:&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;unlinkFirst&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;(&lt;/span&gt;&lt;span class=&quot;n&quot;&gt;f&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;);&lt;/span&gt;
    &lt;span class=&quot;o&quot;&gt;}&lt;/span&gt;

    &lt;span class=&quot;nd&quot;&gt;@Override&lt;/span&gt;
    &lt;span class=&quot;kd&quot;&gt;public&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;E&lt;/span&gt; &lt;span class=&quot;nf&quot;&gt;pollLast&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;()&lt;/span&gt; &lt;span class=&quot;o&quot;&gt;{&lt;/span&gt;
        &lt;span class=&quot;kd&quot;&gt;final&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;Node&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;&amp;lt;&lt;/span&gt;&lt;span class=&quot;n&quot;&gt;E&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;&amp;gt;&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;l&lt;/span&gt; &lt;span class=&quot;o&quot;&gt;=&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;last&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;;&lt;/span&gt;
        &lt;span class=&quot;k&quot;&gt;return&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;l&lt;/span&gt; &lt;span class=&quot;o&quot;&gt;==&lt;/span&gt; &lt;span class=&quot;kc&quot;&gt;null&lt;/span&gt; &lt;span class=&quot;o&quot;&gt;?&lt;/span&gt; &lt;span class=&quot;kc&quot;&gt;null&lt;/span&gt; &lt;span class=&quot;o&quot;&gt;:&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;unlinkLast&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;(&lt;/span&gt;&lt;span class=&quot;n&quot;&gt;l&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;);&lt;/span&gt;
    &lt;span class=&quot;o&quot;&gt;}&lt;/span&gt;

    &lt;span class=&quot;c1&quot;&gt;//get~方法抛出异常&lt;/span&gt;
    &lt;span class=&quot;nd&quot;&gt;@Override&lt;/span&gt;
    &lt;span class=&quot;kd&quot;&gt;public&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;E&lt;/span&gt; &lt;span class=&quot;nf&quot;&gt;getFirst&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;()&lt;/span&gt; &lt;span class=&quot;o&quot;&gt;{&lt;/span&gt;
        &lt;span class=&quot;kd&quot;&gt;final&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;Node&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;&amp;lt;&lt;/span&gt;&lt;span class=&quot;n&quot;&gt;E&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;&amp;gt;&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;f&lt;/span&gt; &lt;span class=&quot;o&quot;&gt;=&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;first&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;;&lt;/span&gt;
        &lt;span class=&quot;k&quot;&gt;if&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;(&lt;/span&gt;&lt;span class=&quot;n&quot;&gt;f&lt;/span&gt; &lt;span class=&quot;o&quot;&gt;==&lt;/span&gt; &lt;span class=&quot;kc&quot;&gt;null&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;)&lt;/span&gt;
            &lt;span class=&quot;k&quot;&gt;throw&lt;/span&gt; &lt;span class=&quot;k&quot;&gt;new&lt;/span&gt; &lt;span class=&quot;nf&quot;&gt;NoSuchElementException&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;();&lt;/span&gt;
        &lt;span class=&quot;k&quot;&gt;return&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;f&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;.&lt;/span&gt;&lt;span class=&quot;na&quot;&gt;item&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;;&lt;/span&gt;
    &lt;span class=&quot;o&quot;&gt;}&lt;/span&gt;

    &lt;span class=&quot;nd&quot;&gt;@Override&lt;/span&gt;
    &lt;span class=&quot;kd&quot;&gt;public&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;E&lt;/span&gt; &lt;span class=&quot;nf&quot;&gt;getLast&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;()&lt;/span&gt; &lt;span class=&quot;o&quot;&gt;{&lt;/span&gt;
        &lt;span class=&quot;kd&quot;&gt;final&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;Node&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;&amp;lt;&lt;/span&gt;&lt;span class=&quot;n&quot;&gt;E&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;&amp;gt;&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;l&lt;/span&gt; &lt;span class=&quot;o&quot;&gt;=&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;last&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;;&lt;/span&gt;
        &lt;span class=&quot;k&quot;&gt;if&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;(&lt;/span&gt;&lt;span class=&quot;n&quot;&gt;l&lt;/span&gt; &lt;span class=&quot;o&quot;&gt;==&lt;/span&gt; &lt;span class=&quot;kc&quot;&gt;null&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;)&lt;/span&gt;
            &lt;span class=&quot;k&quot;&gt;throw&lt;/span&gt; &lt;span class=&quot;k&quot;&gt;new&lt;/span&gt; &lt;span class=&quot;nf&quot;&gt;NoSuchElementException&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;();&lt;/span&gt;
        &lt;span class=&quot;k&quot;&gt;return&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;l&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;.&lt;/span&gt;&lt;span class=&quot;na&quot;&gt;item&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;;&lt;/span&gt;
    &lt;span class=&quot;o&quot;&gt;}&lt;/span&gt;

    &lt;span class=&quot;nd&quot;&gt;@Override&lt;/span&gt;
    &lt;span class=&quot;kd&quot;&gt;public&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;E&lt;/span&gt; &lt;span class=&quot;nf&quot;&gt;peekFirst&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;()&lt;/span&gt; &lt;span class=&quot;o&quot;&gt;{&lt;/span&gt;
        &lt;span class=&quot;kd&quot;&gt;final&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;Node&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;&amp;lt;&lt;/span&gt;&lt;span class=&quot;n&quot;&gt;E&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;&amp;gt;&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;f&lt;/span&gt; &lt;span class=&quot;o&quot;&gt;=&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;first&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;;&lt;/span&gt;
        &lt;span class=&quot;k&quot;&gt;return&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;f&lt;/span&gt; &lt;span class=&quot;o&quot;&gt;==&lt;/span&gt; &lt;span class=&quot;kc&quot;&gt;null&lt;/span&gt; &lt;span class=&quot;o&quot;&gt;?&lt;/span&gt; &lt;span class=&quot;kc&quot;&gt;null&lt;/span&gt; &lt;span class=&quot;o&quot;&gt;:&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;f&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;.&lt;/span&gt;&lt;span class=&quot;na&quot;&gt;item&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;;&lt;/span&gt;
    &lt;span class=&quot;o&quot;&gt;}&lt;/span&gt;

    &lt;span class=&quot;nd&quot;&gt;@Override&lt;/span&gt;
    &lt;span class=&quot;kd&quot;&gt;public&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;E&lt;/span&gt; &lt;span class=&quot;nf&quot;&gt;peekLast&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;()&lt;/span&gt; &lt;span class=&quot;o&quot;&gt;{&lt;/span&gt;
        &lt;span class=&quot;kd&quot;&gt;final&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;Node&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;&amp;lt;&lt;/span&gt;&lt;span class=&quot;n&quot;&gt;E&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;&amp;gt;&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;l&lt;/span&gt; &lt;span class=&quot;o&quot;&gt;=&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;last&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;;&lt;/span&gt;
        &lt;span class=&quot;k&quot;&gt;return&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;l&lt;/span&gt; &lt;span class=&quot;o&quot;&gt;==&lt;/span&gt; &lt;span class=&quot;kc&quot;&gt;null&lt;/span&gt; &lt;span class=&quot;o&quot;&gt;?&lt;/span&gt; &lt;span class=&quot;kc&quot;&gt;null&lt;/span&gt; &lt;span class=&quot;o&quot;&gt;:&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;l&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;.&lt;/span&gt;&lt;span class=&quot;na&quot;&gt;item&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;;&lt;/span&gt;
    &lt;span class=&quot;o&quot;&gt;}&lt;/span&gt;

    &lt;span class=&quot;c1&quot;&gt;//删除队列中第一个该对象的引用&lt;/span&gt;
    &lt;span class=&quot;nd&quot;&gt;@Override&lt;/span&gt;
    &lt;span class=&quot;kd&quot;&gt;public&lt;/span&gt; &lt;span class=&quot;kt&quot;&gt;boolean&lt;/span&gt; &lt;span class=&quot;nf&quot;&gt;removeFirstOccurrence&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;(&lt;/span&gt;&lt;span class=&quot;n&quot;&gt;Object&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;o&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;)&lt;/span&gt; &lt;span class=&quot;o&quot;&gt;{&lt;/span&gt;
        &lt;span class=&quot;k&quot;&gt;return&lt;/span&gt; &lt;span class=&quot;nf&quot;&gt;remove&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;(&lt;/span&gt;&lt;span class=&quot;n&quot;&gt;o&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;);&lt;/span&gt;
    &lt;span class=&quot;o&quot;&gt;}&lt;/span&gt;

    &lt;span class=&quot;c1&quot;&gt;//删除队列中最后一个该对象的引用&lt;/span&gt;
    &lt;span class=&quot;nd&quot;&gt;@Override&lt;/span&gt;
    &lt;span class=&quot;kd&quot;&gt;public&lt;/span&gt; &lt;span class=&quot;kt&quot;&gt;boolean&lt;/span&gt; &lt;span class=&quot;nf&quot;&gt;removeLastOccurrence&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;(&lt;/span&gt;&lt;span class=&quot;n&quot;&gt;Object&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;o&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;)&lt;/span&gt; &lt;span class=&quot;o&quot;&gt;{&lt;/span&gt;
        &lt;span class=&quot;k&quot;&gt;if&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;(&lt;/span&gt;&lt;span class=&quot;n&quot;&gt;o&lt;/span&gt; &lt;span class=&quot;o&quot;&gt;==&lt;/span&gt; &lt;span class=&quot;kc&quot;&gt;null&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;)&lt;/span&gt; &lt;span class=&quot;o&quot;&gt;{&lt;/span&gt;
            &lt;span class=&quot;k&quot;&gt;for&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;(&lt;/span&gt;&lt;span class=&quot;n&quot;&gt;Node&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;&amp;lt;&lt;/span&gt;&lt;span class=&quot;n&quot;&gt;E&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;&amp;gt;&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;x&lt;/span&gt; &lt;span class=&quot;o&quot;&gt;=&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;last&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;;&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;x&lt;/span&gt; &lt;span class=&quot;o&quot;&gt;!=&lt;/span&gt; &lt;span class=&quot;kc&quot;&gt;null&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;;&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;x&lt;/span&gt; &lt;span class=&quot;o&quot;&gt;=&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;x&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;.&lt;/span&gt;&lt;span class=&quot;na&quot;&gt;prev&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;)&lt;/span&gt; &lt;span class=&quot;o&quot;&gt;{&lt;/span&gt;
                &lt;span class=&quot;k&quot;&gt;if&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;(&lt;/span&gt;&lt;span class=&quot;n&quot;&gt;x&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;.&lt;/span&gt;&lt;span class=&quot;na&quot;&gt;item&lt;/span&gt; &lt;span class=&quot;o&quot;&gt;==&lt;/span&gt; &lt;span class=&quot;kc&quot;&gt;null&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;)&lt;/span&gt; &lt;span class=&quot;o&quot;&gt;{&lt;/span&gt;
                    &lt;span class=&quot;n&quot;&gt;unlink&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;(&lt;/span&gt;&lt;span class=&quot;n&quot;&gt;x&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;);&lt;/span&gt;
                    &lt;span class=&quot;k&quot;&gt;return&lt;/span&gt; &lt;span class=&quot;kc&quot;&gt;true&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;;&lt;/span&gt;
                &lt;span class=&quot;o&quot;&gt;}&lt;/span&gt;
            &lt;span class=&quot;o&quot;&gt;}&lt;/span&gt;
        &lt;span class=&quot;o&quot;&gt;}&lt;/span&gt; &lt;span class=&quot;k&quot;&gt;else&lt;/span&gt; &lt;span class=&quot;o&quot;&gt;{&lt;/span&gt;
            &lt;span class=&quot;k&quot;&gt;for&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;(&lt;/span&gt;&lt;span class=&quot;n&quot;&gt;Node&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;&amp;lt;&lt;/span&gt;&lt;span class=&quot;n&quot;&gt;E&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;&amp;gt;&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;x&lt;/span&gt; &lt;span class=&quot;o&quot;&gt;=&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;last&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;;&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;x&lt;/span&gt; &lt;span class=&quot;o&quot;&gt;!=&lt;/span&gt; &lt;span class=&quot;kc&quot;&gt;null&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;;&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;x&lt;/span&gt; &lt;span class=&quot;o&quot;&gt;=&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;x&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;.&lt;/span&gt;&lt;span class=&quot;na&quot;&gt;prev&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;)&lt;/span&gt; &lt;span class=&quot;o&quot;&gt;{&lt;/span&gt;
                &lt;span class=&quot;k&quot;&gt;if&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;(&lt;/span&gt;&lt;span class=&quot;n&quot;&gt;o&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;.&lt;/span&gt;&lt;span class=&quot;na&quot;&gt;equals&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;(&lt;/span&gt;&lt;span class=&quot;n&quot;&gt;x&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;.&lt;/span&gt;&lt;span class=&quot;na&quot;&gt;item&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;))&lt;/span&gt; &lt;span class=&quot;o&quot;&gt;{&lt;/span&gt;
                    &lt;span class=&quot;n&quot;&gt;unlink&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;(&lt;/span&gt;&lt;span class=&quot;n&quot;&gt;x&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;);&lt;/span&gt;
                    &lt;span class=&quot;k&quot;&gt;return&lt;/span&gt; &lt;span class=&quot;kc&quot;&gt;true&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;;&lt;/span&gt;
                &lt;span class=&quot;o&quot;&gt;}&lt;/span&gt;
            &lt;span class=&quot;o&quot;&gt;}&lt;/span&gt;
        &lt;span class=&quot;o&quot;&gt;}&lt;/span&gt;
        &lt;span class=&quot;k&quot;&gt;return&lt;/span&gt; &lt;span class=&quot;kc&quot;&gt;false&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;;&lt;/span&gt;
    &lt;span class=&quot;o&quot;&gt;}&lt;/span&gt;

    &lt;span class=&quot;c1&quot;&gt;//入队操作，链表尾部插入，不抛出异常&lt;/span&gt;
    &lt;span class=&quot;nd&quot;&gt;@Override&lt;/span&gt;
    &lt;span class=&quot;kd&quot;&gt;public&lt;/span&gt; &lt;span class=&quot;kt&quot;&gt;boolean&lt;/span&gt; &lt;span class=&quot;nf&quot;&gt;offer&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;(&lt;/span&gt;&lt;span class=&quot;n&quot;&gt;E&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;e&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;)&lt;/span&gt; &lt;span class=&quot;o&quot;&gt;{&lt;/span&gt;
        &lt;span class=&quot;k&quot;&gt;return&lt;/span&gt; &lt;span class=&quot;nf&quot;&gt;add&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;(&lt;/span&gt;&lt;span class=&quot;n&quot;&gt;e&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;);&lt;/span&gt;
    &lt;span class=&quot;o&quot;&gt;}&lt;/span&gt;

    &lt;span class=&quot;c1&quot;&gt;//出队操作，不抛出异常&lt;/span&gt;
    &lt;span class=&quot;nd&quot;&gt;@Override&lt;/span&gt;
    &lt;span class=&quot;kd&quot;&gt;public&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;E&lt;/span&gt; &lt;span class=&quot;nf&quot;&gt;poll&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;()&lt;/span&gt; &lt;span class=&quot;o&quot;&gt;{&lt;/span&gt;
        &lt;span class=&quot;kd&quot;&gt;final&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;Node&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;&amp;lt;&lt;/span&gt;&lt;span class=&quot;n&quot;&gt;E&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;&amp;gt;&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;f&lt;/span&gt; &lt;span class=&quot;o&quot;&gt;=&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;first&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;;&lt;/span&gt;
        &lt;span class=&quot;k&quot;&gt;return&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;f&lt;/span&gt; &lt;span class=&quot;o&quot;&gt;==&lt;/span&gt; &lt;span class=&quot;kc&quot;&gt;null&lt;/span&gt; &lt;span class=&quot;o&quot;&gt;?&lt;/span&gt; &lt;span class=&quot;kc&quot;&gt;null&lt;/span&gt; &lt;span class=&quot;o&quot;&gt;:&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;unlinkFirst&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;(&lt;/span&gt;&lt;span class=&quot;n&quot;&gt;f&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;);&lt;/span&gt;
    &lt;span class=&quot;o&quot;&gt;}&lt;/span&gt;

    &lt;span class=&quot;c1&quot;&gt;//获取表头元素，栈的操作，不抛出异常&lt;/span&gt;
    &lt;span class=&quot;nd&quot;&gt;@Override&lt;/span&gt;
    &lt;span class=&quot;kd&quot;&gt;public&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;E&lt;/span&gt; &lt;span class=&quot;nf&quot;&gt;peek&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;()&lt;/span&gt; &lt;span class=&quot;o&quot;&gt;{&lt;/span&gt;
        &lt;span class=&quot;kd&quot;&gt;final&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;Node&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;&amp;lt;&lt;/span&gt;&lt;span class=&quot;n&quot;&gt;E&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;&amp;gt;&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;f&lt;/span&gt; &lt;span class=&quot;o&quot;&gt;=&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;first&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;;&lt;/span&gt;
        &lt;span class=&quot;k&quot;&gt;return&lt;/span&gt; &lt;span class=&quot;o&quot;&gt;(&lt;/span&gt;&lt;span class=&quot;n&quot;&gt;f&lt;/span&gt; &lt;span class=&quot;o&quot;&gt;==&lt;/span&gt; &lt;span class=&quot;kc&quot;&gt;null&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;)&lt;/span&gt; &lt;span class=&quot;o&quot;&gt;?&lt;/span&gt; &lt;span class=&quot;kc&quot;&gt;null&lt;/span&gt; &lt;span class=&quot;o&quot;&gt;:&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;f&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;.&lt;/span&gt;&lt;span class=&quot;na&quot;&gt;item&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;;&lt;/span&gt;
    &lt;span class=&quot;o&quot;&gt;}&lt;/span&gt;

    &lt;span class=&quot;c1&quot;&gt;//出队删除，检查抛出异常&lt;/span&gt;
    &lt;span class=&quot;nd&quot;&gt;@Override&lt;/span&gt;
    &lt;span class=&quot;kd&quot;&gt;public&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;E&lt;/span&gt; &lt;span class=&quot;nf&quot;&gt;remove&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;()&lt;/span&gt; &lt;span class=&quot;o&quot;&gt;{&lt;/span&gt;
        &lt;span class=&quot;k&quot;&gt;return&lt;/span&gt; &lt;span class=&quot;nf&quot;&gt;removeFirst&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;();&lt;/span&gt;
    &lt;span class=&quot;o&quot;&gt;}&lt;/span&gt;

    &lt;span class=&quot;c1&quot;&gt;//获取表头元素，抛出异常&lt;/span&gt;
    &lt;span class=&quot;nd&quot;&gt;@Override&lt;/span&gt;
    &lt;span class=&quot;kd&quot;&gt;public&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;E&lt;/span&gt; &lt;span class=&quot;nf&quot;&gt;element&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;()&lt;/span&gt; &lt;span class=&quot;o&quot;&gt;{&lt;/span&gt;
        &lt;span class=&quot;k&quot;&gt;return&lt;/span&gt; &lt;span class=&quot;nf&quot;&gt;getFirst&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;();&lt;/span&gt;
    &lt;span class=&quot;o&quot;&gt;}&lt;/span&gt;

    &lt;span class=&quot;c1&quot;&gt;//入栈，表头添加，栈的操作&lt;/span&gt;
    &lt;span class=&quot;nd&quot;&gt;@Override&lt;/span&gt;
    &lt;span class=&quot;kd&quot;&gt;public&lt;/span&gt; &lt;span class=&quot;kt&quot;&gt;void&lt;/span&gt; &lt;span class=&quot;nf&quot;&gt;push&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;(&lt;/span&gt;&lt;span class=&quot;n&quot;&gt;E&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;e&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;)&lt;/span&gt; &lt;span class=&quot;o&quot;&gt;{&lt;/span&gt;
        &lt;span class=&quot;n&quot;&gt;addFirst&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;(&lt;/span&gt;&lt;span class=&quot;n&quot;&gt;e&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;);&lt;/span&gt;
    &lt;span class=&quot;o&quot;&gt;}&lt;/span&gt;

    &lt;span class=&quot;c1&quot;&gt;//出栈，表头删除，栈的操作&lt;/span&gt;
    &lt;span class=&quot;nd&quot;&gt;@Override&lt;/span&gt;
    &lt;span class=&quot;kd&quot;&gt;public&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;E&lt;/span&gt; &lt;span class=&quot;nf&quot;&gt;pop&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;()&lt;/span&gt; &lt;span class=&quot;o&quot;&gt;{&lt;/span&gt;
        &lt;span class=&quot;k&quot;&gt;return&lt;/span&gt; &lt;span class=&quot;nf&quot;&gt;removeFirst&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;();&lt;/span&gt;
    &lt;span class=&quot;o&quot;&gt;}&lt;/span&gt;
&lt;/code&gt;&lt;/pre&gt;
        &lt;/div&gt;
      &lt;/li&gt;
    &lt;/ul&gt;
  &lt;/li&gt;
  &lt;li&gt;3-5 AbstractSequentialList的实现（实现逆序迭代器）。
    &lt;div class=&quot;language-java highlighter-rouge&quot;&gt;&lt;pre class=&quot;highlight&quot;&gt;&lt;code&gt;      &lt;span class=&quot;c1&quot;&gt;//逆序迭代器&lt;/span&gt;
      &lt;span class=&quot;nd&quot;&gt;@Override&lt;/span&gt;
      &lt;span class=&quot;kd&quot;&gt;public&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;Iterator&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;&amp;lt;&lt;/span&gt;&lt;span class=&quot;n&quot;&gt;E&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;&amp;gt;&lt;/span&gt; &lt;span class=&quot;nf&quot;&gt;descendingIterator&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;()&lt;/span&gt; &lt;span class=&quot;o&quot;&gt;{&lt;/span&gt;
          &lt;span class=&quot;k&quot;&gt;return&lt;/span&gt; &lt;span class=&quot;k&quot;&gt;new&lt;/span&gt; &lt;span class=&quot;nf&quot;&gt;DescendingIterator&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;();&lt;/span&gt;
      &lt;span class=&quot;o&quot;&gt;}&lt;/span&gt;
      &lt;span class=&quot;kd&quot;&gt;private&lt;/span&gt; &lt;span class=&quot;kd&quot;&gt;class&lt;/span&gt; &lt;span class=&quot;nc&quot;&gt;DescendingIterator&lt;/span&gt; &lt;span class=&quot;kd&quot;&gt;implements&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;Iterator&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;&amp;lt;&lt;/span&gt;&lt;span class=&quot;n&quot;&gt;E&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;&amp;gt;&lt;/span&gt; &lt;span class=&quot;o&quot;&gt;{&lt;/span&gt;
          &lt;span class=&quot;kd&quot;&gt;private&lt;/span&gt; &lt;span class=&quot;kd&quot;&gt;final&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;ListItr&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;itr&lt;/span&gt; &lt;span class=&quot;o&quot;&gt;=&lt;/span&gt; &lt;span class=&quot;k&quot;&gt;new&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;ListItr&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;(&lt;/span&gt;&lt;span class=&quot;n&quot;&gt;size&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;());&lt;/span&gt;
          &lt;span class=&quot;kd&quot;&gt;public&lt;/span&gt; &lt;span class=&quot;kt&quot;&gt;boolean&lt;/span&gt; &lt;span class=&quot;nf&quot;&gt;hasNext&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;()&lt;/span&gt; &lt;span class=&quot;o&quot;&gt;{&lt;/span&gt;
              &lt;span class=&quot;k&quot;&gt;return&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;itr&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;.&lt;/span&gt;&lt;span class=&quot;na&quot;&gt;hasPrevious&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;();&lt;/span&gt;
          &lt;span class=&quot;o&quot;&gt;}&lt;/span&gt;
          &lt;span class=&quot;kd&quot;&gt;public&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;E&lt;/span&gt; &lt;span class=&quot;nf&quot;&gt;next&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;()&lt;/span&gt; &lt;span class=&quot;o&quot;&gt;{&lt;/span&gt;
              &lt;span class=&quot;k&quot;&gt;return&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;itr&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;.&lt;/span&gt;&lt;span class=&quot;na&quot;&gt;previous&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;();&lt;/span&gt;
          &lt;span class=&quot;o&quot;&gt;}&lt;/span&gt;
          &lt;span class=&quot;kd&quot;&gt;public&lt;/span&gt; &lt;span class=&quot;kt&quot;&gt;void&lt;/span&gt; &lt;span class=&quot;nf&quot;&gt;remove&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;()&lt;/span&gt; &lt;span class=&quot;o&quot;&gt;{&lt;/span&gt;
              &lt;span class=&quot;n&quot;&gt;itr&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;.&lt;/span&gt;&lt;span class=&quot;na&quot;&gt;remove&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;();&lt;/span&gt;
          &lt;span class=&quot;o&quot;&gt;}&lt;/span&gt;
      &lt;span class=&quot;o&quot;&gt;}&lt;/span&gt;
&lt;/code&gt;&lt;/pre&gt;
    &lt;/div&gt;
  &lt;/li&gt;
  &lt;li&gt;3-6 Cloneable的实现
    &lt;div class=&quot;language-java highlighter-rouge&quot;&gt;&lt;pre class=&quot;highlight&quot;&gt;&lt;code&gt;      &lt;span class=&quot;nd&quot;&gt;@Override&lt;/span&gt;
      &lt;span class=&quot;kd&quot;&gt;public&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;Object&lt;/span&gt; &lt;span class=&quot;nf&quot;&gt;clone&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;()&lt;/span&gt; &lt;span class=&quot;o&quot;&gt;{&lt;/span&gt;
          &lt;span class=&quot;n&quot;&gt;MLinkedList&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;&amp;lt;&lt;/span&gt;&lt;span class=&quot;n&quot;&gt;E&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;&amp;gt;&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;clone&lt;/span&gt; &lt;span class=&quot;o&quot;&gt;=&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;superClone&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;();&lt;/span&gt;
          &lt;span class=&quot;n&quot;&gt;clone&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;.&lt;/span&gt;&lt;span class=&quot;na&quot;&gt;first&lt;/span&gt; &lt;span class=&quot;o&quot;&gt;=&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;clone&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;.&lt;/span&gt;&lt;span class=&quot;na&quot;&gt;last&lt;/span&gt; &lt;span class=&quot;o&quot;&gt;=&lt;/span&gt; &lt;span class=&quot;kc&quot;&gt;null&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;;&lt;/span&gt;
          &lt;span class=&quot;n&quot;&gt;clone&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;.&lt;/span&gt;&lt;span class=&quot;na&quot;&gt;size&lt;/span&gt; &lt;span class=&quot;o&quot;&gt;=&lt;/span&gt; &lt;span class=&quot;mi&quot;&gt;0&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;;&lt;/span&gt;
          &lt;span class=&quot;n&quot;&gt;clone&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;.&lt;/span&gt;&lt;span class=&quot;na&quot;&gt;modCount&lt;/span&gt; &lt;span class=&quot;o&quot;&gt;=&lt;/span&gt; &lt;span class=&quot;mi&quot;&gt;0&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;;&lt;/span&gt;

          &lt;span class=&quot;k&quot;&gt;for&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;(&lt;/span&gt;&lt;span class=&quot;n&quot;&gt;Node&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;&amp;lt;&lt;/span&gt;&lt;span class=&quot;n&quot;&gt;E&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;&amp;gt;&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;x&lt;/span&gt; &lt;span class=&quot;o&quot;&gt;=&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;first&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;;&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;x&lt;/span&gt; &lt;span class=&quot;o&quot;&gt;!=&lt;/span&gt; &lt;span class=&quot;kc&quot;&gt;null&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;;&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;x&lt;/span&gt; &lt;span class=&quot;o&quot;&gt;=&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;x&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;.&lt;/span&gt;&lt;span class=&quot;na&quot;&gt;next&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;)&lt;/span&gt; &lt;span class=&quot;o&quot;&gt;{&lt;/span&gt;
              &lt;span class=&quot;n&quot;&gt;clone&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;.&lt;/span&gt;&lt;span class=&quot;na&quot;&gt;add&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;(&lt;/span&gt;&lt;span class=&quot;n&quot;&gt;x&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;.&lt;/span&gt;&lt;span class=&quot;na&quot;&gt;item&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;);&lt;/span&gt;
          &lt;span class=&quot;o&quot;&gt;}&lt;/span&gt;

          &lt;span class=&quot;k&quot;&gt;return&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;clone&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;;&lt;/span&gt;
      &lt;span class=&quot;o&quot;&gt;}&lt;/span&gt;

      &lt;span class=&quot;nd&quot;&gt;@SuppressWarnings&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;(&lt;/span&gt;&lt;span class=&quot;s&quot;&gt;&quot;unchecked&quot;&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;)&lt;/span&gt;
      &lt;span class=&quot;kd&quot;&gt;private&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;MLinkedList&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;&amp;lt;&lt;/span&gt;&lt;span class=&quot;n&quot;&gt;E&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;&amp;gt;&lt;/span&gt; &lt;span class=&quot;nf&quot;&gt;superClone&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;()&lt;/span&gt; &lt;span class=&quot;o&quot;&gt;{&lt;/span&gt;
          &lt;span class=&quot;k&quot;&gt;try&lt;/span&gt; &lt;span class=&quot;o&quot;&gt;{&lt;/span&gt;
              &lt;span class=&quot;k&quot;&gt;return&lt;/span&gt; &lt;span class=&quot;o&quot;&gt;(&lt;/span&gt;&lt;span class=&quot;n&quot;&gt;MLinkedList&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;&amp;lt;&lt;/span&gt;&lt;span class=&quot;n&quot;&gt;E&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;&amp;gt;)&lt;/span&gt; &lt;span class=&quot;kd&quot;&gt;super&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;.&lt;/span&gt;&lt;span class=&quot;na&quot;&gt;clone&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;();&lt;/span&gt;
          &lt;span class=&quot;o&quot;&gt;}&lt;/span&gt; &lt;span class=&quot;k&quot;&gt;catch&lt;/span&gt; &lt;span class=&quot;o&quot;&gt;(&lt;/span&gt;&lt;span class=&quot;n&quot;&gt;CloneNotSupportedException&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;e&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;)&lt;/span&gt; &lt;span class=&quot;o&quot;&gt;{&lt;/span&gt;
              &lt;span class=&quot;k&quot;&gt;throw&lt;/span&gt; &lt;span class=&quot;k&quot;&gt;new&lt;/span&gt; &lt;span class=&quot;nf&quot;&gt;InternalError&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;(&lt;/span&gt;&lt;span class=&quot;n&quot;&gt;e&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;);&lt;/span&gt;
          &lt;span class=&quot;o&quot;&gt;}&lt;/span&gt;
      &lt;span class=&quot;o&quot;&gt;}&lt;/span&gt;
&lt;/code&gt;&lt;/pre&gt;
    &lt;/div&gt;
  &lt;/li&gt;
  &lt;li&gt;3-7 序列化支持
    &lt;ul&gt;
      &lt;li&gt;3-7-1 LinkedList的size，first，last使用transient关键字，使用自定义的序列化机制，只写入size和元素对象，一方面是隐藏内部表示信息，一方面节省了开销；&lt;/li&gt;
      &lt;li&gt;3-7-2 在JDK1.7之前使用的并不是Node而是Entry，也是保存了元素对象而不是Entry，这样的考虑解决了LinkedList的兼容问题；
        &lt;div class=&quot;language-java highlighter-rouge&quot;&gt;&lt;pre class=&quot;highlight&quot;&gt;&lt;code&gt;    &lt;span class=&quot;c1&quot;&gt;//序列化版本号，是数据域和方法签名的数字指纹（SHA）&lt;/span&gt;
    &lt;span class=&quot;kd&quot;&gt;private&lt;/span&gt; &lt;span class=&quot;kd&quot;&gt;static&lt;/span&gt; &lt;span class=&quot;kd&quot;&gt;final&lt;/span&gt; &lt;span class=&quot;kt&quot;&gt;long&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;serialVersionUID&lt;/span&gt; &lt;span class=&quot;o&quot;&gt;=&lt;/span&gt; &lt;span class=&quot;mi&quot;&gt;876323262645176354L&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;;&lt;/span&gt;

    &lt;span class=&quot;c1&quot;&gt;//代替默认的序列化过程，这里值写入了元素对象和元素集合大小&lt;/span&gt;
    &lt;span class=&quot;c1&quot;&gt;//在JDK1.7之前使用的并不是Node而是Entry，也是保存了元素对象而不是Entry，这样的考虑解决了LinkedList的兼容问题&lt;/span&gt;
    &lt;span class=&quot;c1&quot;&gt;//这也是为什么用transient修饰size，first，last域的原因&lt;/span&gt;
    &lt;span class=&quot;c1&quot;&gt;//一方面是隐藏内部表示信息，一方面节省了开销&lt;/span&gt;
    &lt;span class=&quot;kd&quot;&gt;private&lt;/span&gt; &lt;span class=&quot;kt&quot;&gt;void&lt;/span&gt; &lt;span class=&quot;nf&quot;&gt;writeObject&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;(&lt;/span&gt;&lt;span class=&quot;n&quot;&gt;java&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;.&lt;/span&gt;&lt;span class=&quot;na&quot;&gt;io&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;.&lt;/span&gt;&lt;span class=&quot;na&quot;&gt;ObjectOutputStream&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;s&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;)&lt;/span&gt;
            &lt;span class=&quot;kd&quot;&gt;throws&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;IOException&lt;/span&gt; &lt;span class=&quot;o&quot;&gt;{&lt;/span&gt;
        &lt;span class=&quot;c1&quot;&gt;//写入包括魔数，序列化格式版本号，包括所有对象的类型和（非静态和非transient）数据域&lt;/span&gt;
        &lt;span class=&quot;c1&quot;&gt;//每个对象包括一个序列号&lt;/span&gt;
        &lt;span class=&quot;c1&quot;&gt;//相同对象重复出现将被视为对这个对象序列号的引用&lt;/span&gt;
        &lt;span class=&quot;n&quot;&gt;s&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;.&lt;/span&gt;&lt;span class=&quot;na&quot;&gt;defaultWriteObject&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;();&lt;/span&gt;

        &lt;span class=&quot;n&quot;&gt;s&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;.&lt;/span&gt;&lt;span class=&quot;na&quot;&gt;writeInt&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;(&lt;/span&gt;&lt;span class=&quot;n&quot;&gt;size&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;);&lt;/span&gt;

        &lt;span class=&quot;k&quot;&gt;for&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;(&lt;/span&gt;&lt;span class=&quot;n&quot;&gt;Node&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;&amp;lt;&lt;/span&gt;&lt;span class=&quot;n&quot;&gt;E&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;&amp;gt;&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;x&lt;/span&gt; &lt;span class=&quot;o&quot;&gt;=&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;first&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;;&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;x&lt;/span&gt; &lt;span class=&quot;o&quot;&gt;!=&lt;/span&gt; &lt;span class=&quot;kc&quot;&gt;null&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;;&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;x&lt;/span&gt; &lt;span class=&quot;o&quot;&gt;=&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;x&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;.&lt;/span&gt;&lt;span class=&quot;na&quot;&gt;next&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;)&lt;/span&gt; &lt;span class=&quot;o&quot;&gt;{&lt;/span&gt;
            &lt;span class=&quot;n&quot;&gt;s&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;.&lt;/span&gt;&lt;span class=&quot;na&quot;&gt;writeObject&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;(&lt;/span&gt;&lt;span class=&quot;n&quot;&gt;x&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;.&lt;/span&gt;&lt;span class=&quot;na&quot;&gt;item&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;);&lt;/span&gt;
        &lt;span class=&quot;o&quot;&gt;}&lt;/span&gt;
    &lt;span class=&quot;o&quot;&gt;}&lt;/span&gt;

    &lt;span class=&quot;c1&quot;&gt;//反序列化过程，同样读取size和元素对象，重新“构建”链表&lt;/span&gt;
    &lt;span class=&quot;nd&quot;&gt;@SuppressWarnings&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;(&lt;/span&gt;&lt;span class=&quot;s&quot;&gt;&quot;unchecked&quot;&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;)&lt;/span&gt;
    &lt;span class=&quot;kd&quot;&gt;private&lt;/span&gt; &lt;span class=&quot;kt&quot;&gt;void&lt;/span&gt; &lt;span class=&quot;nf&quot;&gt;readObject&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;(&lt;/span&gt;&lt;span class=&quot;n&quot;&gt;java&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;.&lt;/span&gt;&lt;span class=&quot;na&quot;&gt;io&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;.&lt;/span&gt;&lt;span class=&quot;na&quot;&gt;ObjectInputStream&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;s&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;)&lt;/span&gt;
            &lt;span class=&quot;kd&quot;&gt;throws&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;IOException&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;,&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;ClassNotFoundException&lt;/span&gt; &lt;span class=&quot;o&quot;&gt;{&lt;/span&gt;
        &lt;span class=&quot;n&quot;&gt;s&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;.&lt;/span&gt;&lt;span class=&quot;na&quot;&gt;defaultReadObject&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;();&lt;/span&gt;

        &lt;span class=&quot;kt&quot;&gt;int&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;size&lt;/span&gt; &lt;span class=&quot;o&quot;&gt;=&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;s&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;.&lt;/span&gt;&lt;span class=&quot;na&quot;&gt;readInt&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;();&lt;/span&gt;

        &lt;span class=&quot;k&quot;&gt;for&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;(&lt;/span&gt;&lt;span class=&quot;kt&quot;&gt;int&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;i&lt;/span&gt; &lt;span class=&quot;o&quot;&gt;=&lt;/span&gt; &lt;span class=&quot;mi&quot;&gt;0&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;;&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;i&lt;/span&gt; &lt;span class=&quot;o&quot;&gt;&amp;lt;&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;size&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;;&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;i&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;++)&lt;/span&gt; &lt;span class=&quot;o&quot;&gt;{&lt;/span&gt;
            &lt;span class=&quot;n&quot;&gt;linkLast&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;((&lt;/span&gt;&lt;span class=&quot;n&quot;&gt;E&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;)&lt;/span&gt;&lt;span class=&quot;n&quot;&gt;s&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;.&lt;/span&gt;&lt;span class=&quot;na&quot;&gt;readObject&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;());&lt;/span&gt;
        &lt;span class=&quot;o&quot;&gt;}&lt;/span&gt;
    &lt;span class=&quot;o&quot;&gt;}&lt;/span&gt;
&lt;/code&gt;&lt;/pre&gt;
        &lt;/div&gt;
        &lt;ol&gt;
          &lt;li&gt;LinkedList对Java 8新特性的支持（例如对Lambda表达式的支持）&lt;/li&gt;
        &lt;/ol&gt;
      &lt;/li&gt;
    &lt;/ul&gt;
  &lt;/li&gt;
&lt;/ul&gt;

&lt;ol&gt;
  &lt;li&gt;总结：
    &lt;ul&gt;
      &lt;li&gt;LinkedList 是一个继承于AbstractSequentialList的双向链表。它也可以被当作堆栈、队列或双端队列进行操作。&lt;/li&gt;
      &lt;li&gt;LinkedList 实现 List 接口，能对它进行队列操作。&lt;/li&gt;
      &lt;li&gt;LinkedList 实现 Deque 接口，即能将LinkedList当作双端队列使用。&lt;/li&gt;
      &lt;li&gt;LinkedList 实现了Cloneable接口，即覆盖了函数clone()，能克隆。&lt;/li&gt;
      &lt;li&gt;LinkedList 实现java.io.Serializable接口，这意味着LinkedList支持序列化，能通过序列化去传输。&lt;/li&gt;
      &lt;li&gt;LinkedList 是非同步的。&lt;/li&gt;
    &lt;/ul&gt;
  &lt;/li&gt;
&lt;/ol&gt;

&lt;ul&gt;
  &lt;li&gt;LinkedList的本质是双向链表。&lt;/li&gt;
  &lt;li&gt;LinkedList继承于AbstractSequentialList，并且实现了Dequeue接口。&lt;/li&gt;
  &lt;li&gt;LinkedList包含两个重要的成员：header 和 size。
　　+ header是双向链表的表头，它是双向链表节点所对应的类Entry的实例。Entry中包含成员变量： previous, next, element。其中，previous是该节点的上一个节点，next是该节点的下一个节点，element是该节点所包含的值。
　　+ size是双向链表中节点的个数。&lt;/li&gt;
  &lt;li&gt;LinkedList 实际上是通过双向链表去实现的。
      它包含一个非常重要的内部类：Entry。Entry是双向链表节点所对应的数据结构，它包括的属性有：当前节点所包含的值，上一个节点，下一个节点。&lt;/li&gt;
  &lt;li&gt;从LinkedList的实现方式中可以发现，它不存在LinkedList容量不足的问题。&lt;/li&gt;
  &lt;li&gt;LinkedList的克隆函数，即是将全部元素克隆到一个新的LinkedList对象中。&lt;/li&gt;
  &lt;li&gt;LinkedList实现java.io.Serializable。当写入到输出流时，先写入“容量”，再依次写入“每一个节点保护的值”；当读出输入流时，先读取“容量”，再依次读取“每一个元素”。&lt;/li&gt;
  &lt;li&gt;由于LinkedList实现了Deque，而Deque接口定义了在双端队列两端访问元素的方法。提供插入、移除和检查元素的方法。每种方法都存在两种形式：一种形式在操作失败时抛出异常，另一种形式返回一个特殊值（null 或 false，具体取决于操作）。&lt;/li&gt;
  &lt;li&gt;LinkedList可以作为FIFO(先进先出)的队列，作为FIFO的队列时，下表的方法等价：&lt;/li&gt;
&lt;/ul&gt;

&lt;table&gt;
  &lt;thead&gt;
    &lt;tr&gt;
      &lt;th&gt;队列方法&lt;/th&gt;
      &lt;th style=&quot;text-align: center&quot;&gt;等效方法&lt;/th&gt;
    &lt;/tr&gt;
    &lt;tr&gt;
      &lt;th&gt;add(e)&lt;/th&gt;
      &lt;th style=&quot;text-align: center&quot;&gt;addLast(e)&lt;/th&gt;
    &lt;/tr&gt;
  &lt;/thead&gt;
  &lt;tbody&gt;
    &lt;tr&gt;
      &lt;td&gt;offer(e)&lt;/td&gt;
      &lt;td style=&quot;text-align: center&quot;&gt;offerLast(e)&lt;/td&gt;
    &lt;/tr&gt;
    &lt;tr&gt;
      &lt;td&gt;remove()&lt;/td&gt;
      &lt;td style=&quot;text-align: center&quot;&gt;removeFirst()&lt;/td&gt;
    &lt;/tr&gt;
    &lt;tr&gt;
      &lt;td&gt;poll()&lt;/td&gt;
      &lt;td style=&quot;text-align: center&quot;&gt;pollFirst()&lt;/td&gt;
    &lt;/tr&gt;
    &lt;tr&gt;
      &lt;td&gt;element()&lt;/td&gt;
      &lt;td style=&quot;text-align: center&quot;&gt;getFirst()&lt;/td&gt;
    &lt;/tr&gt;
    &lt;tr&gt;
      &lt;td&gt;peek()&lt;/td&gt;
      &lt;td style=&quot;text-align: center&quot;&gt;peekFirst()&lt;/td&gt;
    &lt;/tr&gt;
  &lt;/tbody&gt;
&lt;/table&gt;

&lt;ul&gt;
  &lt;li&gt;LinkedList可以作为LIFO(后进先出)的栈，作为LIFO的栈时，下表的方法等价：&lt;/li&gt;
&lt;/ul&gt;

&lt;table&gt;
  &lt;thead&gt;
    &lt;tr&gt;
      &lt;th&gt;栈方法&lt;/th&gt;
      &lt;th style=&quot;text-align: center&quot;&gt;等效方法&lt;/th&gt;
    &lt;/tr&gt;
  &lt;/thead&gt;
  &lt;tbody&gt;
    &lt;tr&gt;
      &lt;td&gt;push(e)&lt;/td&gt;
      &lt;td style=&quot;text-align: center&quot;&gt;addFirst(e)&lt;/td&gt;
    &lt;/tr&gt;
    &lt;tr&gt;
      &lt;td&gt;pop()&lt;/td&gt;
      &lt;td style=&quot;text-align: center&quot;&gt;removeFirst()&lt;/td&gt;
    &lt;/tr&gt;
    &lt;tr&gt;
      &lt;td&gt;peek()&lt;/td&gt;
      &lt;td style=&quot;text-align: center&quot;&gt;peekFirst()&lt;/td&gt;
    &lt;/tr&gt;
  &lt;/tbody&gt;
&lt;/table&gt;

&lt;p&gt;&lt;strong&gt;与Stack比较&lt;/strong&gt;&lt;/p&gt;

&lt;p&gt;Stack是栈。它的特性是：先进后出(FILO, First In Last Out)。
java工具包中的Stack是继承于Vector(矢量队列)的，由于Vector是通过数组实现的，这就意味着，Stack也是通过数组实现的，而非链表。当然，我们也可以将LinkedList当作栈来使用！在“Java 集合系列06之 Vector详细介绍(源码解析)和使用示例”中，已经详细介绍过Vector的数据结构，这里就不再对Stack的数据结构进行说明了。&lt;/p&gt;
&lt;ol&gt;
  &lt;li&gt;Stack实际上也是通过数组去实现的。
    执行push时(即，将元素推入栈中)，是通过将元素追加的数组的末尾中。
    执行peek时(即，取出栈顶元素，不执行删除)，是返回数组末尾的元素。
    执行pop时(即，取出栈顶元素，并将该元素从栈中删除)，是取出数组末尾的元素，然后将该元素从数组中删除。&lt;/li&gt;
  &lt;li&gt;Stack继承于Vector，意味着Vector拥有的属性和功能，Stack都拥有。&lt;/li&gt;
&lt;/ol&gt;</content><category term="JavaBasic" /><summary type="html">LinkedList源码分析.</summary></entry><entry><title type="html">Java源码分析——ArrayList</title><link href="https://ckape.github.io/workhard/ArrayList/" rel="alternate" type="text/html" title="Java源码分析——ArrayList" /><published>2016-09-20T00:00:00+08:00</published><updated>2016-09-20T00:00:00+08:00</updated><id>https://ckape.github.io/workhard/ArrayList</id><content type="html" xml:base="https://ckape.github.io/workhard/ArrayList/">&lt;h1 id=&quot;list&quot;&gt;List&lt;/h1&gt;
&lt;ol&gt;
  &lt;li&gt;&lt;strong&gt;ArrayList（常用）&lt;/strong&gt;
    &lt;ul&gt;
      &lt;li&gt;Serializable&lt;/li&gt;
      &lt;li&gt;Cloneable&lt;/li&gt;
      &lt;li&gt;Iterable&lt;E&gt;&lt;/E&gt;&lt;/li&gt;
      &lt;li&gt;Collection&lt;E&gt;&lt;/E&gt;&lt;/li&gt;
      &lt;li&gt;List&lt;E&gt;&lt;/E&gt;&lt;/li&gt;
      &lt;li&gt;RandomAccess&lt;/li&gt;
    &lt;/ul&gt;
  &lt;/li&gt;
  &lt;li&gt;&lt;strong&gt;LinkedList（常用）&lt;/strong&gt;
    &lt;ul&gt;
      &lt;li&gt;Serializable&lt;/li&gt;
      &lt;li&gt;Cloneable&lt;/li&gt;
      &lt;li&gt;Iterable&lt;E&gt;&lt;/E&gt;&lt;/li&gt;
      &lt;li&gt;Collection&lt;E&gt;&lt;/E&gt;&lt;/li&gt;
      &lt;li&gt;Deque&lt;E&gt;&lt;/E&gt;&lt;/li&gt;
      &lt;li&gt;List&lt;E&gt;&lt;/E&gt;&lt;/li&gt;
      &lt;li&gt;Queue&lt;E&gt;&lt;/E&gt;&lt;/li&gt;
    &lt;/ul&gt;
  &lt;/li&gt;
  &lt;li&gt;&lt;strong&gt;Stack（了解）&lt;/strong&gt;&lt;/li&gt;
  &lt;li&gt;&lt;strong&gt;CopyOnWriteArrayList&lt;/strong&gt;&lt;/li&gt;
  &lt;li&gt;&lt;strong&gt;AbstractList&lt;/strong&gt;&lt;/li&gt;
  &lt;li&gt;&lt;strong&gt;Vector&lt;/strong&gt;&lt;/li&gt;
&lt;/ol&gt;

&lt;h2 id=&quot;arraylist&quot;&gt;ArrayList&lt;/h2&gt;
&lt;p&gt;modCount : The number of times this list has been structurally modified. Structural modifications are those that change the size of the list, or otherwise perturb it in such a fashion that iterations in progress may yield incorrect results.（已从结构上修改此列表的次数。从结构上修改是指更改列表的大小，或者打乱列表，从而使正在进行的迭代产生错误的结果。）&lt;/p&gt;

&lt;ol&gt;
  &lt;li&gt;要点
    &lt;ul&gt;
      &lt;li&gt;&lt;strong&gt;基于数组实现&lt;/strong&gt;：内部表示通过控制对象数组的访问，数组是不能动态修改大小的，因此根据元素数量/指定容量大小，通过创建新数组，复制元素对象是ArrayList的核心原理之一；&lt;/li&gt;
      &lt;li&gt;&lt;strong&gt;性能特点&lt;/strong&gt;：因为基于数组的，因此可以实现快速随机访问，比LinkedList效率高；但是增加/删除等需要通过复制数组元素（部分或全部）来实现，效率比LinkedList低；&lt;/li&gt;
      &lt;li&gt;&lt;strong&gt;线程不安全&lt;/strong&gt;：同样使用 modCount 修改计数，类似 乐观锁 的 &lt;code class=&quot;highlighter-rouge&quot;&gt;fail-fast&lt;/code&gt; （一种错误机制） 来防止并发修改带来的不一致，ArrayList的每个Iterator，ListIterator，SubList实例都独立维护一个基于ArrayList实例modCount的expectedModCount；可以使用Collections.synchronizedList进行锁定&lt;/li&gt;
      &lt;li&gt;&lt;strong&gt;优化手段&lt;/strong&gt;：
        &lt;ul&gt;
          &lt;li&gt;单例模式：&lt;strong&gt;EMPTY_ELEMENTDATA&lt;/strong&gt; 和 &lt;strong&gt;DEFAULTCAPACITY_EMPTY_ELEMENTDATA&lt;/strong&gt; 这两个单例的空数组对象，分别被空状态和默认状态的ArrayList共享；&lt;/li&gt;
          &lt;li&gt;grow方法的增长机制 ：每次扩展数组的大小至少扩展到原数据的3/2大小，减少了创建新数组和复制动作的次数；&lt;/li&gt;
        &lt;/ul&gt;
      &lt;/li&gt;
      &lt;li&gt;&lt;strong&gt;克隆和序列化&lt;/strong&gt;：实现了Serializable和Cloneable接口，支持序列化和克隆，其中序列化使用writeObject和readObject不采用默认的序列化机制，只保存size和元素对象，一方面是隐藏内部表示信息，一方面节省了开销；&lt;/li&gt;
      &lt;li&gt;&lt;strong&gt;防止内存泄漏的置空动作&lt;/strong&gt;：维护一个数组也是自己维护内存管理，因为数组也持有这引用，删除时要及时置空不能影响GC活动；&lt;/li&gt;
    &lt;/ul&gt;
  &lt;/li&gt;
  &lt;li&gt;基本结构和操作
    &lt;ul&gt;
      &lt;li&gt;重要属性
        &lt;div class=&quot;language-java highlighter-rouge&quot;&gt;&lt;pre class=&quot;highlight&quot;&gt;&lt;code&gt;  &lt;span class=&quot;c1&quot;&gt;//默认初始化容量&lt;/span&gt;
  &lt;span class=&quot;kd&quot;&gt;private&lt;/span&gt; &lt;span class=&quot;kd&quot;&gt;static&lt;/span&gt; &lt;span class=&quot;kd&quot;&gt;final&lt;/span&gt; &lt;span class=&quot;kt&quot;&gt;int&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;DEFAULT_CAPACITY&lt;/span&gt; &lt;span class=&quot;o&quot;&gt;=&lt;/span&gt; &lt;span class=&quot;mi&quot;&gt;10&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;;&lt;/span&gt;
  &lt;span class=&quot;cm&quot;&gt;/*
      所有Empty数组列表共享一个空数组对象，不仅可以减少重复对象的创建（单例模式应用），
还可以标识空列表状态单例模式（区别于享元模式）：
      一是这里只有一个对象；
      二是不仅仅是节省内存，更重要的是起到共享并标识“空数组列表”的作用；
      EMPTY_ELEMENTDATA标识“空”状态，DEFAULTCAPACITY_EMPTY_ELEMENTDATA标识默认状态
      */&lt;/span&gt;
  &lt;span class=&quot;kd&quot;&gt;private&lt;/span&gt; &lt;span class=&quot;kd&quot;&gt;static&lt;/span&gt; &lt;span class=&quot;kd&quot;&gt;final&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;Object&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;[]&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;EMPTY_ELEMENTDATA&lt;/span&gt; &lt;span class=&quot;o&quot;&gt;=&lt;/span&gt; &lt;span class=&quot;o&quot;&gt;{};&lt;/span&gt;
  &lt;span class=&quot;cm&quot;&gt;/*
      默认状态创建数组列表实例使用该数组，使用一个单例空数组并且不直接使用
EMPTY_ELEMENTDATA而是新键一个空数组的原因是：
      一是用于标识不同的状态，区别于“空数组列表”，
DEFAULTCAPACITY_EMPTY_ELEMENTDATA表示数组列表还未插入元素；
      二是等到实际有元素再分配合适大小的数组内存空间，起到延迟加载的作用；
      三是同样单例可以让所有默认状态列表使用一个空数组对象，节省内存；
  */&lt;/span&gt;
  &lt;span class=&quot;kd&quot;&gt;private&lt;/span&gt; &lt;span class=&quot;kd&quot;&gt;static&lt;/span&gt; &lt;span class=&quot;kd&quot;&gt;final&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;Object&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;[]&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;DEFAULTCAPACITY_EMPTY_ELEMENTDATA&lt;/span&gt; &lt;span class=&quot;o&quot;&gt;=&lt;/span&gt; &lt;span class=&quot;o&quot;&gt;{};&lt;/span&gt;
  &lt;span class=&quot;cm&quot;&gt;/*
  使用transient的目的是为了隐藏内部表示
  使用Object的原因：
  （1）Object可以引用所有具体类型的数组对象；
  （2）实际的ArrayList的类型参数对于ArrayList对象本身是不可知的，
   泛型的本质是擦除，并借助变量，方法，类的签名来进行类型检查和转换;
  因此可以用Object数组存放元素对象，依赖方法和类型参数让编译器和JVM进行类型检查和转换
 （比如插入checkcast指令等等）；
      */&lt;/span&gt;
  &lt;span class=&quot;kd&quot;&gt;transient&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;Object&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;[]&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;elementData&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;;&lt;/span&gt;
  &lt;span class=&quot;c1&quot;&gt;//元素个数&lt;/span&gt;
  &lt;span class=&quot;kd&quot;&gt;private&lt;/span&gt; &lt;span class=&quot;kt&quot;&gt;int&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;size&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;;&lt;/span&gt;
  &lt;span class=&quot;cm&quot;&gt;/*
  一些实现可能会保存一些首部信息在数组对象中。
  试图分配一个比MAX_ARRAY_SIZE大的数组可能会造成OOM
 （Requested array size exceeds VM limit）。
  也就是说一些JVM的实现可能会限制数组大小小于Integer.MAX_VALUE，因此检查是必要的。
      */&lt;/span&gt;
  &lt;span class=&quot;kd&quot;&gt;private&lt;/span&gt; &lt;span class=&quot;kd&quot;&gt;static&lt;/span&gt; &lt;span class=&quot;kd&quot;&gt;final&lt;/span&gt; &lt;span class=&quot;kt&quot;&gt;int&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;MAX_ARRAY_SIZE&lt;/span&gt; &lt;span class=&quot;o&quot;&gt;=&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;Integer&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;.&lt;/span&gt;&lt;span class=&quot;na&quot;&gt;MAX_VALUE&lt;/span&gt; &lt;span class=&quot;o&quot;&gt;-&lt;/span&gt; &lt;span class=&quot;mi&quot;&gt;8&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;;&lt;/span&gt;
&lt;/code&gt;&lt;/pre&gt;
        &lt;/div&gt;
      &lt;/li&gt;
      &lt;li&gt;不同版本的构造器
        &lt;ol&gt;
          &lt;li&gt;ArrayList()：默认状态，使用DEFAULTCAPACITY_EMPTY_ELEMENTDATA，这也是一个空数组，延迟加载，第一次插入时才分配内存；&lt;/li&gt;
          &lt;li&gt;如果指定的初始化容量为0,拷贝构造器传入集合为空，使用EMPTY_ELEMENTDATA；
            &lt;div class=&quot;language-java highlighter-rouge&quot;&gt;&lt;pre class=&quot;highlight&quot;&gt;&lt;code&gt; &lt;span class=&quot;c1&quot;&gt;//如果指定初始化容量为“0”，使用EMPTY_ELEMENTDATA&lt;/span&gt;
 &lt;span class=&quot;kd&quot;&gt;public&lt;/span&gt; &lt;span class=&quot;nf&quot;&gt;ArrayList&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;(&lt;/span&gt;&lt;span class=&quot;kt&quot;&gt;int&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;initialCapacity&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;)&lt;/span&gt; &lt;span class=&quot;o&quot;&gt;{&lt;/span&gt;
 &lt;span class=&quot;k&quot;&gt;if&lt;/span&gt; &lt;span class=&quot;o&quot;&gt;(&lt;/span&gt;&lt;span class=&quot;n&quot;&gt;initialCapacity&lt;/span&gt; &lt;span class=&quot;o&quot;&gt;&amp;gt;&lt;/span&gt; &lt;span class=&quot;mi&quot;&gt;0&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;)&lt;/span&gt; &lt;span class=&quot;o&quot;&gt;{&lt;/span&gt;
   &lt;span class=&quot;k&quot;&gt;this&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;.&lt;/span&gt;&lt;span class=&quot;na&quot;&gt;elementData&lt;/span&gt; &lt;span class=&quot;o&quot;&gt;=&lt;/span&gt; &lt;span class=&quot;k&quot;&gt;new&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;Object&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;[&lt;/span&gt;&lt;span class=&quot;n&quot;&gt;initialCapacity&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;];&lt;/span&gt;
 &lt;span class=&quot;o&quot;&gt;}&lt;/span&gt; &lt;span class=&quot;k&quot;&gt;else&lt;/span&gt; &lt;span class=&quot;k&quot;&gt;if&lt;/span&gt; &lt;span class=&quot;o&quot;&gt;(&lt;/span&gt;&lt;span class=&quot;n&quot;&gt;initialCapacity&lt;/span&gt; &lt;span class=&quot;o&quot;&gt;==&lt;/span&gt; &lt;span class=&quot;mi&quot;&gt;0&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;)&lt;/span&gt; &lt;span class=&quot;o&quot;&gt;{&lt;/span&gt;
   &lt;span class=&quot;k&quot;&gt;this&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;.&lt;/span&gt;&lt;span class=&quot;na&quot;&gt;elementData&lt;/span&gt; &lt;span class=&quot;o&quot;&gt;=&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;EMPTY_ELEMENTDATA&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;;&lt;/span&gt;
 &lt;span class=&quot;o&quot;&gt;}&lt;/span&gt; &lt;span class=&quot;k&quot;&gt;else&lt;/span&gt; &lt;span class=&quot;o&quot;&gt;{&lt;/span&gt;
   &lt;span class=&quot;k&quot;&gt;throw&lt;/span&gt; &lt;span class=&quot;k&quot;&gt;new&lt;/span&gt; &lt;span class=&quot;nf&quot;&gt;IllegalArgumentException&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;(&lt;/span&gt;&lt;span class=&quot;s&quot;&gt;&quot;Illegal Capacity: &quot;&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;+&lt;/span&gt;
         &lt;span class=&quot;n&quot;&gt;initialCapacity&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;);&lt;/span&gt;
 &lt;span class=&quot;o&quot;&gt;}&lt;/span&gt;
 &lt;span class=&quot;o&quot;&gt;}&lt;/span&gt;
 &lt;span class=&quot;c1&quot;&gt;//创建默认初始化容量列表，使用DEFAULTCAPACITY_EMPTY_ELEMENTDATA&lt;/span&gt;
 &lt;span class=&quot;kd&quot;&gt;public&lt;/span&gt; &lt;span class=&quot;nf&quot;&gt;ArrayList&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;()&lt;/span&gt; &lt;span class=&quot;o&quot;&gt;{&lt;/span&gt;
   &lt;span class=&quot;k&quot;&gt;this&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;.&lt;/span&gt;&lt;span class=&quot;na&quot;&gt;elementData&lt;/span&gt; &lt;span class=&quot;o&quot;&gt;=&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;DEFAULTCAPACITY_EMPTY_ELEMENTDATA&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;;&lt;/span&gt;
 &lt;span class=&quot;o&quot;&gt;}&lt;/span&gt;
 &lt;span class=&quot;c1&quot;&gt;//拷贝构造器，注意使用toArray获取要插入元素对象&lt;/span&gt;
 &lt;span class=&quot;kd&quot;&gt;public&lt;/span&gt; &lt;span class=&quot;nf&quot;&gt;ArrayList&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;(&lt;/span&gt;&lt;span class=&quot;n&quot;&gt;Collection&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;&amp;lt;?&lt;/span&gt; &lt;span class=&quot;kd&quot;&gt;extends&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;E&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;&amp;gt;&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;c&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;)&lt;/span&gt; &lt;span class=&quot;o&quot;&gt;{&lt;/span&gt;
 &lt;span class=&quot;n&quot;&gt;elementData&lt;/span&gt; &lt;span class=&quot;o&quot;&gt;=&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;c&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;.&lt;/span&gt;&lt;span class=&quot;na&quot;&gt;toArray&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;();&lt;/span&gt;
 &lt;span class=&quot;k&quot;&gt;if&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;((&lt;/span&gt;&lt;span class=&quot;n&quot;&gt;size&lt;/span&gt; &lt;span class=&quot;o&quot;&gt;=&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;elementData&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;.&lt;/span&gt;&lt;span class=&quot;na&quot;&gt;length&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;)&lt;/span&gt; &lt;span class=&quot;o&quot;&gt;!=&lt;/span&gt; &lt;span class=&quot;mi&quot;&gt;0&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;)&lt;/span&gt; &lt;span class=&quot;o&quot;&gt;{&lt;/span&gt;
 &lt;span class=&quot;cm&quot;&gt;/*
 注意，toArray返回的Object[]引用，
 而Object[]可以作为超类引用子类对象比如A[]（假设A是E的子类）
 如果toArray返回是A[]数组对象，那么如果类型B对象（B extends E）
 可能会引起后续的插入时的ArrayStoreException，读取元素时的ClassCheckException
 因此如果返回的不是Object[]对象，要创建一个Object[]并复制元素引用
  */&lt;/span&gt;
 &lt;span class=&quot;k&quot;&gt;if&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;(&lt;/span&gt;&lt;span class=&quot;n&quot;&gt;elementData&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;.&lt;/span&gt;&lt;span class=&quot;na&quot;&gt;getClass&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;()&lt;/span&gt; &lt;span class=&quot;o&quot;&gt;!=&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;Object&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;[].&lt;/span&gt;&lt;span class=&quot;na&quot;&gt;class&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;)&lt;/span&gt; &lt;span class=&quot;o&quot;&gt;{&lt;/span&gt;
     &lt;span class=&quot;n&quot;&gt;elementData&lt;/span&gt; &lt;span class=&quot;o&quot;&gt;=&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;Arrays&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;.&lt;/span&gt;&lt;span class=&quot;na&quot;&gt;copyOf&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;(&lt;/span&gt;&lt;span class=&quot;n&quot;&gt;elementData&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;,&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;size&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;,&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;Objects&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;[].&lt;/span&gt;&lt;span class=&quot;na&quot;&gt;class&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;);&lt;/span&gt;
 &lt;span class=&quot;o&quot;&gt;}&lt;/span&gt;
 &lt;span class=&quot;o&quot;&gt;}&lt;/span&gt; &lt;span class=&quot;k&quot;&gt;else&lt;/span&gt; &lt;span class=&quot;o&quot;&gt;{&lt;/span&gt;
 &lt;span class=&quot;c1&quot;&gt;//一个空数组列表，直接使用EMPTY_ELEMENTDATA&lt;/span&gt;
 &lt;span class=&quot;n&quot;&gt;elementData&lt;/span&gt; &lt;span class=&quot;o&quot;&gt;=&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;EMPTY_ELEMENTDATA&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;;&lt;/span&gt;
 &lt;span class=&quot;o&quot;&gt;}&lt;/span&gt;
 &lt;span class=&quot;o&quot;&gt;}&lt;/span&gt;
&lt;/code&gt;&lt;/pre&gt;
            &lt;/div&gt;
          &lt;/li&gt;
        &lt;/ol&gt;
      &lt;/li&gt;
      &lt;li&gt;核心操作&lt;/li&gt;
    &lt;/ul&gt;
  &lt;/li&gt;
  &lt;li&gt;主要方法包括：trimToSize（压缩缓存数组），grow（扩展容量），ensure～（不同情况下调用的扩容方法），removeRange（范围删除），batchRemove（批量删除），fastRemove（基于复制的快速复制），这些方法供之后方法调用；&lt;/li&gt;
&lt;/ol&gt;

&lt;div class=&quot;language-java highlighter-rouge&quot;&gt;&lt;pre class=&quot;highlight&quot;&gt;&lt;code&gt;    &lt;span class=&quot;c1&quot;&gt;//压缩缓存区大小，最小化存储区域到size相同的大小&lt;/span&gt;
    &lt;span class=&quot;kd&quot;&gt;public&lt;/span&gt; &lt;span class=&quot;kt&quot;&gt;void&lt;/span&gt; &lt;span class=&quot;nf&quot;&gt;trimToSize&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;()&lt;/span&gt; &lt;span class=&quot;o&quot;&gt;{&lt;/span&gt;
        &lt;span class=&quot;n&quot;&gt;modCount&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;++;&lt;/span&gt;
        &lt;span class=&quot;k&quot;&gt;if&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;(&lt;/span&gt;&lt;span class=&quot;n&quot;&gt;size&lt;/span&gt; &lt;span class=&quot;o&quot;&gt;&amp;lt;&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;elementData&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;.&lt;/span&gt;&lt;span class=&quot;na&quot;&gt;length&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;)&lt;/span&gt; &lt;span class=&quot;o&quot;&gt;{&lt;/span&gt;
            &lt;span class=&quot;n&quot;&gt;elementData&lt;/span&gt; &lt;span class=&quot;o&quot;&gt;=&lt;/span&gt; &lt;span class=&quot;o&quot;&gt;(&lt;/span&gt;&lt;span class=&quot;n&quot;&gt;size&lt;/span&gt; &lt;span class=&quot;o&quot;&gt;==&lt;/span&gt; &lt;span class=&quot;mi&quot;&gt;0&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;)&lt;/span&gt;
                    &lt;span class=&quot;o&quot;&gt;?&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;EMPTY_ELEMENTDATA&lt;/span&gt;
                    &lt;span class=&quot;o&quot;&gt;:&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;Arrays&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;.&lt;/span&gt;&lt;span class=&quot;na&quot;&gt;copyOf&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;(&lt;/span&gt;&lt;span class=&quot;n&quot;&gt;elementData&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;,&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;size&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;);&lt;/span&gt;
        &lt;span class=&quot;o&quot;&gt;}&lt;/span&gt;
    &lt;span class=&quot;o&quot;&gt;}&lt;/span&gt;
    &lt;span class=&quot;c1&quot;&gt;//增加容量到指定大小（溢出会抛出OOM），通过这个方法可以打破MAX_ARRAY_SIZE限制&lt;/span&gt;
    &lt;span class=&quot;kd&quot;&gt;private&lt;/span&gt; &lt;span class=&quot;kt&quot;&gt;void&lt;/span&gt; &lt;span class=&quot;nf&quot;&gt;grow&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;(&lt;/span&gt;&lt;span class=&quot;kt&quot;&gt;int&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;minCapacity&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;)&lt;/span&gt; &lt;span class=&quot;o&quot;&gt;{&lt;/span&gt;
        &lt;span class=&quot;c1&quot;&gt;// overflow-conscious code&lt;/span&gt;
        &lt;span class=&quot;kt&quot;&gt;int&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;oldCapacity&lt;/span&gt; &lt;span class=&quot;o&quot;&gt;=&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;elementData&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;.&lt;/span&gt;&lt;span class=&quot;na&quot;&gt;length&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;;&lt;/span&gt;
        &lt;span class=&quot;c1&quot;&gt;//首先尝试将新容量设置为原容量的（3/2）&lt;/span&gt;
        &lt;span class=&quot;c1&quot;&gt;//这样做可以避免频繁小幅度的扩张带来的开销，我联想到一个类似的做法是滑动窗口中修改窗口大小的机制&lt;/span&gt;
        &lt;span class=&quot;kt&quot;&gt;int&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;newCapacity&lt;/span&gt; &lt;span class=&quot;o&quot;&gt;=&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;oldCapacity&lt;/span&gt; &lt;span class=&quot;o&quot;&gt;+&lt;/span&gt; &lt;span class=&quot;o&quot;&gt;(&lt;/span&gt;&lt;span class=&quot;n&quot;&gt;oldCapacity&lt;/span&gt; &lt;span class=&quot;o&quot;&gt;&amp;gt;&amp;gt;&lt;/span&gt; &lt;span class=&quot;mi&quot;&gt;1&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;);&lt;/span&gt;
        &lt;span class=&quot;c1&quot;&gt;//如果尚未达到指定大小（这说明扩张幅度够大），设置为指定大小&lt;/span&gt;
        &lt;span class=&quot;k&quot;&gt;if&lt;/span&gt; &lt;span class=&quot;o&quot;&gt;(&lt;/span&gt;&lt;span class=&quot;n&quot;&gt;newCapacity&lt;/span&gt; &lt;span class=&quot;o&quot;&gt;-&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;minCapacity&lt;/span&gt; &lt;span class=&quot;o&quot;&gt;&amp;lt;&lt;/span&gt; &lt;span class=&quot;mi&quot;&gt;0&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;)&lt;/span&gt;
            &lt;span class=&quot;n&quot;&gt;newCapacity&lt;/span&gt; &lt;span class=&quot;o&quot;&gt;=&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;minCapacity&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;;&lt;/span&gt;
        &lt;span class=&quot;k&quot;&gt;if&lt;/span&gt; &lt;span class=&quot;o&quot;&gt;(&lt;/span&gt;&lt;span class=&quot;n&quot;&gt;newCapacity&lt;/span&gt; &lt;span class=&quot;o&quot;&gt;-&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;MAX_ARRAY_SIZE&lt;/span&gt; &lt;span class=&quot;o&quot;&gt;&amp;gt;&lt;/span&gt; &lt;span class=&quot;mi&quot;&gt;0&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;)&lt;/span&gt;
            &lt;span class=&quot;n&quot;&gt;newCapacity&lt;/span&gt; &lt;span class=&quot;o&quot;&gt;=&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;hugeCapacity&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;(&lt;/span&gt;&lt;span class=&quot;n&quot;&gt;minCapacity&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;);&lt;/span&gt;
        &lt;span class=&quot;c1&quot;&gt;// minCapacity is usually close to size, so this is a win:&lt;/span&gt;
        &lt;span class=&quot;n&quot;&gt;elementData&lt;/span&gt; &lt;span class=&quot;o&quot;&gt;=&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;Arrays&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;.&lt;/span&gt;&lt;span class=&quot;na&quot;&gt;copyOf&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;(&lt;/span&gt;&lt;span class=&quot;n&quot;&gt;elementData&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;,&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;newCapacity&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;);&lt;/span&gt;
    &lt;span class=&quot;o&quot;&gt;}&lt;/span&gt;
    &lt;span class=&quot;kd&quot;&gt;private&lt;/span&gt; &lt;span class=&quot;kd&quot;&gt;static&lt;/span&gt; &lt;span class=&quot;kt&quot;&gt;int&lt;/span&gt; &lt;span class=&quot;nf&quot;&gt;hugeCapacity&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;(&lt;/span&gt;&lt;span class=&quot;kt&quot;&gt;int&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;minCapacity&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;)&lt;/span&gt; &lt;span class=&quot;o&quot;&gt;{&lt;/span&gt;
        &lt;span class=&quot;k&quot;&gt;if&lt;/span&gt; &lt;span class=&quot;o&quot;&gt;(&lt;/span&gt;&lt;span class=&quot;n&quot;&gt;minCapacity&lt;/span&gt; &lt;span class=&quot;o&quot;&gt;&amp;lt;&lt;/span&gt; &lt;span class=&quot;mi&quot;&gt;0&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;)&lt;/span&gt; &lt;span class=&quot;c1&quot;&gt;// overflow&lt;/span&gt;
            &lt;span class=&quot;k&quot;&gt;throw&lt;/span&gt; &lt;span class=&quot;k&quot;&gt;new&lt;/span&gt; &lt;span class=&quot;nf&quot;&gt;OutOfMemoryError&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;();&lt;/span&gt;
        &lt;span class=&quot;k&quot;&gt;return&lt;/span&gt; &lt;span class=&quot;o&quot;&gt;(&lt;/span&gt;&lt;span class=&quot;n&quot;&gt;minCapacity&lt;/span&gt; &lt;span class=&quot;o&quot;&gt;&amp;gt;&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;MAX_ARRAY_SIZE&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;)&lt;/span&gt; &lt;span class=&quot;o&quot;&gt;?&lt;/span&gt;
                &lt;span class=&quot;n&quot;&gt;Integer&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;.&lt;/span&gt;&lt;span class=&quot;na&quot;&gt;MAX_VALUE&lt;/span&gt; &lt;span class=&quot;o&quot;&gt;:&lt;/span&gt;
                &lt;span class=&quot;n&quot;&gt;MAX_ARRAY_SIZE&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;;&lt;/span&gt;
    &lt;span class=&quot;o&quot;&gt;}&lt;/span&gt;
    &lt;span class=&quot;c1&quot;&gt;//当ArrayList不处于默认状态时，才可能扩展大小为小于DEFAULT_CAPACITY的容量；&lt;/span&gt;
    &lt;span class=&quot;c1&quot;&gt;// 否则只有指定大小超过DEFAULT_CAPACITY时才进行扩展；&lt;/span&gt;
    &lt;span class=&quot;c1&quot;&gt;//注意这个方法是public，区别于ensureCapacityInternal，这个方法是在外部使用的；&lt;/span&gt;
    &lt;span class=&quot;kd&quot;&gt;public&lt;/span&gt; &lt;span class=&quot;kt&quot;&gt;void&lt;/span&gt; &lt;span class=&quot;nf&quot;&gt;ensureCapacity&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;(&lt;/span&gt;&lt;span class=&quot;kt&quot;&gt;int&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;minCapacity&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;)&lt;/span&gt; &lt;span class=&quot;o&quot;&gt;{&lt;/span&gt;
        &lt;span class=&quot;kt&quot;&gt;int&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;minExpand&lt;/span&gt; &lt;span class=&quot;o&quot;&gt;=&lt;/span&gt; &lt;span class=&quot;o&quot;&gt;(&lt;/span&gt;&lt;span class=&quot;n&quot;&gt;elementData&lt;/span&gt; &lt;span class=&quot;o&quot;&gt;!=&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;DEFAULTCAPACITY_EMPTY_ELEMENTDATA&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;)&lt;/span&gt;
                &lt;span class=&quot;c1&quot;&gt;// any size if not default element table&lt;/span&gt;
                &lt;span class=&quot;o&quot;&gt;?&lt;/span&gt; &lt;span class=&quot;mi&quot;&gt;0&lt;/span&gt;
                &lt;span class=&quot;c1&quot;&gt;// larger than default for default empty table. It's already&lt;/span&gt;
                &lt;span class=&quot;c1&quot;&gt;// supposed to be at default size.&lt;/span&gt;
                &lt;span class=&quot;o&quot;&gt;:&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;DEFAULT_CAPACITY&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;;&lt;/span&gt;

        &lt;span class=&quot;k&quot;&gt;if&lt;/span&gt; &lt;span class=&quot;o&quot;&gt;(&lt;/span&gt;&lt;span class=&quot;n&quot;&gt;minCapacity&lt;/span&gt; &lt;span class=&quot;o&quot;&gt;&amp;gt;&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;minExpand&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;)&lt;/span&gt; &lt;span class=&quot;o&quot;&gt;{&lt;/span&gt;
            &lt;span class=&quot;n&quot;&gt;ensureExplicitCapacity&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;(&lt;/span&gt;&lt;span class=&quot;n&quot;&gt;minCapacity&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;);&lt;/span&gt;
        &lt;span class=&quot;o&quot;&gt;}&lt;/span&gt;
    &lt;span class=&quot;o&quot;&gt;}&lt;/span&gt;
    &lt;span class=&quot;c1&quot;&gt;//ArrayList内部扩展大小使用此方法，没有上个条件方法限制&lt;/span&gt;
    &lt;span class=&quot;c1&quot;&gt;//但如果处于默认状态，扩展大小仍然不能小于DEFAULT_CAPACITY&lt;/span&gt;
    &lt;span class=&quot;kd&quot;&gt;private&lt;/span&gt; &lt;span class=&quot;kt&quot;&gt;void&lt;/span&gt; &lt;span class=&quot;nf&quot;&gt;ensureCapacityInternal&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;(&lt;/span&gt;&lt;span class=&quot;kt&quot;&gt;int&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;minCapacity&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;)&lt;/span&gt; &lt;span class=&quot;o&quot;&gt;{&lt;/span&gt;
        &lt;span class=&quot;k&quot;&gt;if&lt;/span&gt; &lt;span class=&quot;o&quot;&gt;(&lt;/span&gt;&lt;span class=&quot;n&quot;&gt;elementData&lt;/span&gt; &lt;span class=&quot;o&quot;&gt;==&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;DEFAULTCAPACITY_EMPTY_ELEMENTDATA&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;)&lt;/span&gt; &lt;span class=&quot;o&quot;&gt;{&lt;/span&gt;
            &lt;span class=&quot;n&quot;&gt;minCapacity&lt;/span&gt; &lt;span class=&quot;o&quot;&gt;=&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;Math&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;.&lt;/span&gt;&lt;span class=&quot;na&quot;&gt;max&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;(&lt;/span&gt;&lt;span class=&quot;n&quot;&gt;DEFAULT_CAPACITY&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;,&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;minCapacity&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;);&lt;/span&gt;
        &lt;span class=&quot;o&quot;&gt;}&lt;/span&gt;

        &lt;span class=&quot;n&quot;&gt;ensureExplicitCapacity&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;(&lt;/span&gt;&lt;span class=&quot;n&quot;&gt;minCapacity&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;);&lt;/span&gt;
    &lt;span class=&quot;o&quot;&gt;}&lt;/span&gt;
    &lt;span class=&quot;kd&quot;&gt;private&lt;/span&gt; &lt;span class=&quot;kt&quot;&gt;void&lt;/span&gt; &lt;span class=&quot;nf&quot;&gt;ensureExplicitCapacity&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;(&lt;/span&gt;&lt;span class=&quot;kt&quot;&gt;int&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;minCapacity&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;)&lt;/span&gt; &lt;span class=&quot;o&quot;&gt;{&lt;/span&gt;
        &lt;span class=&quot;n&quot;&gt;modCount&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;++;&lt;/span&gt;

        &lt;span class=&quot;c1&quot;&gt;// overflow-conscious code&lt;/span&gt;
        &lt;span class=&quot;k&quot;&gt;if&lt;/span&gt; &lt;span class=&quot;o&quot;&gt;(&lt;/span&gt;&lt;span class=&quot;n&quot;&gt;minCapacity&lt;/span&gt; &lt;span class=&quot;o&quot;&gt;-&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;elementData&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;.&lt;/span&gt;&lt;span class=&quot;na&quot;&gt;length&lt;/span&gt; &lt;span class=&quot;o&quot;&gt;&amp;gt;&lt;/span&gt; &lt;span class=&quot;mi&quot;&gt;0&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;)&lt;/span&gt;
            &lt;span class=&quot;n&quot;&gt;grow&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;(&lt;/span&gt;&lt;span class=&quot;n&quot;&gt;minCapacity&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;);&lt;/span&gt;
    &lt;span class=&quot;o&quot;&gt;}&lt;/span&gt;
    &lt;span class=&quot;c1&quot;&gt;//删除[fromIndex, toIndex)范围的元素&lt;/span&gt;
    &lt;span class=&quot;c1&quot;&gt;//操作后将末尾newSize之后的元素置空，防止内存泄漏&lt;/span&gt;
    &lt;span class=&quot;kd&quot;&gt;protected&lt;/span&gt; &lt;span class=&quot;kt&quot;&gt;void&lt;/span&gt; &lt;span class=&quot;nf&quot;&gt;removeRange&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;(&lt;/span&gt;&lt;span class=&quot;kt&quot;&gt;int&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;fromIndex&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;,&lt;/span&gt; &lt;span class=&quot;kt&quot;&gt;int&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;toIndex&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;)&lt;/span&gt; &lt;span class=&quot;o&quot;&gt;{&lt;/span&gt;
        &lt;span class=&quot;n&quot;&gt;modCount&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;++;&lt;/span&gt; &lt;span class=&quot;c1&quot;&gt;//fail-fast&lt;/span&gt;
        &lt;span class=&quot;kt&quot;&gt;int&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;numMoved&lt;/span&gt; &lt;span class=&quot;o&quot;&gt;=&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;size&lt;/span&gt; &lt;span class=&quot;o&quot;&gt;-&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;toIndex&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;;&lt;/span&gt;
        &lt;span class=&quot;n&quot;&gt;System&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;.&lt;/span&gt;&lt;span class=&quot;na&quot;&gt;arraycopy&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;(&lt;/span&gt;&lt;span class=&quot;n&quot;&gt;elementData&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;,&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;fromIndex&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;,&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;elementData&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;,&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;toIndex&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;,&lt;/span&gt;
                &lt;span class=&quot;n&quot;&gt;numMoved&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;);&lt;/span&gt;

        &lt;span class=&quot;c1&quot;&gt;//清空多余的元素引用&lt;/span&gt;
        &lt;span class=&quot;kt&quot;&gt;int&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;newSize&lt;/span&gt; &lt;span class=&quot;o&quot;&gt;=&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;size&lt;/span&gt; &lt;span class=&quot;o&quot;&gt;-&lt;/span&gt; &lt;span class=&quot;o&quot;&gt;(&lt;/span&gt;&lt;span class=&quot;n&quot;&gt;toIndex&lt;/span&gt; &lt;span class=&quot;o&quot;&gt;-&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;fromIndex&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;);&lt;/span&gt;
        &lt;span class=&quot;k&quot;&gt;for&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;(&lt;/span&gt;&lt;span class=&quot;kt&quot;&gt;int&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;i&lt;/span&gt; &lt;span class=&quot;o&quot;&gt;=&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;newSize&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;;&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;i&lt;/span&gt; &lt;span class=&quot;o&quot;&gt;&amp;lt;&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;size&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;;&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;i&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;++)&lt;/span&gt;
            &lt;span class=&quot;n&quot;&gt;elementData&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;[&lt;/span&gt;&lt;span class=&quot;n&quot;&gt;i&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;]&lt;/span&gt; &lt;span class=&quot;o&quot;&gt;=&lt;/span&gt; &lt;span class=&quot;kc&quot;&gt;null&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;;&lt;/span&gt;
        &lt;span class=&quot;n&quot;&gt;size&lt;/span&gt; &lt;span class=&quot;o&quot;&gt;=&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;newSize&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;;&lt;/span&gt;
    &lt;span class=&quot;o&quot;&gt;}&lt;/span&gt;
    &lt;span class=&quot;c1&quot;&gt;//批量删除，complement为false时删除数组缓冲区中集合c包含的元素，true，删除集合c中不包含的元素，可以用实现交，差等集合运算&lt;/span&gt;
    &lt;span class=&quot;c1&quot;&gt;//使用复制的方法，而不是调用remove()的方式，减少了元素的重复复制&lt;/span&gt;
    &lt;span class=&quot;c1&quot;&gt;//同样要将newSize之外的元素引用置空，防止内存泄漏&lt;/span&gt;
    &lt;span class=&quot;kd&quot;&gt;private&lt;/span&gt; &lt;span class=&quot;kt&quot;&gt;boolean&lt;/span&gt; &lt;span class=&quot;nf&quot;&gt;batchRemove&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;(&lt;/span&gt;&lt;span class=&quot;n&quot;&gt;Collection&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;&amp;lt;?&amp;gt;&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;c&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;,&lt;/span&gt; &lt;span class=&quot;kt&quot;&gt;boolean&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;complement&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;)&lt;/span&gt; &lt;span class=&quot;o&quot;&gt;{&lt;/span&gt;
        &lt;span class=&quot;kd&quot;&gt;final&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;Object&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;[]&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;elementData&lt;/span&gt; &lt;span class=&quot;o&quot;&gt;=&lt;/span&gt; &lt;span class=&quot;k&quot;&gt;this&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;.&lt;/span&gt;&lt;span class=&quot;na&quot;&gt;elementData&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;;&lt;/span&gt;
        &lt;span class=&quot;kt&quot;&gt;int&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;r&lt;/span&gt; &lt;span class=&quot;o&quot;&gt;=&lt;/span&gt; &lt;span class=&quot;mi&quot;&gt;0&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;,&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;w&lt;/span&gt; &lt;span class=&quot;o&quot;&gt;=&lt;/span&gt; &lt;span class=&quot;mi&quot;&gt;0&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;;&lt;/span&gt; &lt;span class=&quot;c1&quot;&gt;//不变式，w &amp;lt;= r&lt;/span&gt;
        &lt;span class=&quot;kt&quot;&gt;boolean&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;modified&lt;/span&gt; &lt;span class=&quot;o&quot;&gt;=&lt;/span&gt; &lt;span class=&quot;kc&quot;&gt;false&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;;&lt;/span&gt;
        &lt;span class=&quot;k&quot;&gt;try&lt;/span&gt; &lt;span class=&quot;o&quot;&gt;{&lt;/span&gt;
            &lt;span class=&quot;k&quot;&gt;for&lt;/span&gt; &lt;span class=&quot;o&quot;&gt;(;&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;r&lt;/span&gt; &lt;span class=&quot;o&quot;&gt;&amp;lt;&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;size&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;;&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;r&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;++)&lt;/span&gt; &lt;span class=&quot;o&quot;&gt;{&lt;/span&gt;
                &lt;span class=&quot;k&quot;&gt;if&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;(&lt;/span&gt;&lt;span class=&quot;n&quot;&gt;c&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;.&lt;/span&gt;&lt;span class=&quot;na&quot;&gt;contains&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;(&lt;/span&gt;&lt;span class=&quot;n&quot;&gt;elementData&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;[&lt;/span&gt;&lt;span class=&quot;n&quot;&gt;r&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;])&lt;/span&gt; &lt;span class=&quot;o&quot;&gt;==&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;complement&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;)&lt;/span&gt; &lt;span class=&quot;o&quot;&gt;{&lt;/span&gt;
                    &lt;span class=&quot;n&quot;&gt;elementData&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;[&lt;/span&gt;&lt;span class=&quot;n&quot;&gt;w&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;++]&lt;/span&gt; &lt;span class=&quot;o&quot;&gt;=&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;elementData&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;[&lt;/span&gt;&lt;span class=&quot;n&quot;&gt;r&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;];&lt;/span&gt;
                &lt;span class=&quot;o&quot;&gt;}&lt;/span&gt;
            &lt;span class=&quot;o&quot;&gt;}&lt;/span&gt;
        &lt;span class=&quot;o&quot;&gt;}&lt;/span&gt; &lt;span class=&quot;k&quot;&gt;finally&lt;/span&gt; &lt;span class=&quot;o&quot;&gt;{&lt;/span&gt;
            &lt;span class=&quot;c1&quot;&gt;//如果有异常抛出，保存好还未处理的数组元素&lt;/span&gt;
            &lt;span class=&quot;k&quot;&gt;if&lt;/span&gt; &lt;span class=&quot;o&quot;&gt;(&lt;/span&gt;&lt;span class=&quot;n&quot;&gt;r&lt;/span&gt; &lt;span class=&quot;o&quot;&gt;!=&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;size&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;)&lt;/span&gt; &lt;span class=&quot;o&quot;&gt;{&lt;/span&gt;
                &lt;span class=&quot;n&quot;&gt;System&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;.&lt;/span&gt;&lt;span class=&quot;na&quot;&gt;arraycopy&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;(&lt;/span&gt;&lt;span class=&quot;n&quot;&gt;elementData&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;,&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;r&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;,&lt;/span&gt;
                        &lt;span class=&quot;n&quot;&gt;elementData&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;,&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;w&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;,&lt;/span&gt;
                        &lt;span class=&quot;n&quot;&gt;size&lt;/span&gt; &lt;span class=&quot;o&quot;&gt;-&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;r&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;);&lt;/span&gt;
                &lt;span class=&quot;n&quot;&gt;w&lt;/span&gt; &lt;span class=&quot;o&quot;&gt;+=&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;size&lt;/span&gt; &lt;span class=&quot;o&quot;&gt;-&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;r&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;;&lt;/span&gt;
            &lt;span class=&quot;o&quot;&gt;}&lt;/span&gt;
            &lt;span class=&quot;k&quot;&gt;if&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;(&lt;/span&gt;&lt;span class=&quot;n&quot;&gt;w&lt;/span&gt; &lt;span class=&quot;o&quot;&gt;!=&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;size&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;)&lt;/span&gt; &lt;span class=&quot;o&quot;&gt;{&lt;/span&gt;
                &lt;span class=&quot;k&quot;&gt;for&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;(&lt;/span&gt;&lt;span class=&quot;kt&quot;&gt;int&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;i&lt;/span&gt; &lt;span class=&quot;o&quot;&gt;=&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;w&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;;&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;i&lt;/span&gt; &lt;span class=&quot;o&quot;&gt;&amp;lt;&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;size&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;;&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;i&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;++)&lt;/span&gt;
                    &lt;span class=&quot;n&quot;&gt;elementData&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;[&lt;/span&gt;&lt;span class=&quot;n&quot;&gt;i&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;]&lt;/span&gt; &lt;span class=&quot;o&quot;&gt;=&lt;/span&gt; &lt;span class=&quot;kc&quot;&gt;null&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;;&lt;/span&gt;
                &lt;span class=&quot;n&quot;&gt;modCount&lt;/span&gt; &lt;span class=&quot;o&quot;&gt;+=&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;size&lt;/span&gt; &lt;span class=&quot;o&quot;&gt;-&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;w&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;;&lt;/span&gt;
                &lt;span class=&quot;n&quot;&gt;size&lt;/span&gt; &lt;span class=&quot;o&quot;&gt;=&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;w&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;;&lt;/span&gt;
                &lt;span class=&quot;n&quot;&gt;modified&lt;/span&gt; &lt;span class=&quot;o&quot;&gt;=&lt;/span&gt; &lt;span class=&quot;kc&quot;&gt;true&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;;&lt;/span&gt;
            &lt;span class=&quot;o&quot;&gt;}&lt;/span&gt;
        &lt;span class=&quot;o&quot;&gt;}&lt;/span&gt;
        &lt;span class=&quot;k&quot;&gt;return&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;modified&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;;&lt;/span&gt;
    &lt;span class=&quot;o&quot;&gt;}&lt;/span&gt;
   &lt;span class=&quot;c1&quot;&gt;//由调用者检查index是否合法&lt;/span&gt;
    &lt;span class=&quot;kd&quot;&gt;private&lt;/span&gt; &lt;span class=&quot;kt&quot;&gt;void&lt;/span&gt; &lt;span class=&quot;nf&quot;&gt;fastRemove&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;(&lt;/span&gt;&lt;span class=&quot;kt&quot;&gt;int&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;index&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;)&lt;/span&gt; &lt;span class=&quot;o&quot;&gt;{&lt;/span&gt;
        &lt;span class=&quot;n&quot;&gt;modCount&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;++;&lt;/span&gt;
        &lt;span class=&quot;kt&quot;&gt;int&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;numMoved&lt;/span&gt; &lt;span class=&quot;o&quot;&gt;=&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;size&lt;/span&gt; &lt;span class=&quot;o&quot;&gt;-&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;index&lt;/span&gt; &lt;span class=&quot;o&quot;&gt;-&lt;/span&gt; &lt;span class=&quot;mi&quot;&gt;1&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;;&lt;/span&gt;
        &lt;span class=&quot;k&quot;&gt;if&lt;/span&gt; &lt;span class=&quot;o&quot;&gt;(&lt;/span&gt;&lt;span class=&quot;n&quot;&gt;numMoved&lt;/span&gt; &lt;span class=&quot;o&quot;&gt;&amp;gt;&lt;/span&gt; &lt;span class=&quot;mi&quot;&gt;0&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;)&lt;/span&gt;
            &lt;span class=&quot;n&quot;&gt;System&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;.&lt;/span&gt;&lt;span class=&quot;na&quot;&gt;arraycopy&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;(&lt;/span&gt;&lt;span class=&quot;n&quot;&gt;elementData&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;,&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;index&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;+&lt;/span&gt;&lt;span class=&quot;mi&quot;&gt;1&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;,&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;elementData&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;,&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;index&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;,&lt;/span&gt;
                    &lt;span class=&quot;n&quot;&gt;numMoved&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;);&lt;/span&gt;
        &lt;span class=&quot;n&quot;&gt;elementData&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;[--&lt;/span&gt;&lt;span class=&quot;n&quot;&gt;size&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;]&lt;/span&gt; &lt;span class=&quot;o&quot;&gt;=&lt;/span&gt; &lt;span class=&quot;kc&quot;&gt;null&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;;&lt;/span&gt; &lt;span class=&quot;c1&quot;&gt;// clear to let GC do its work&lt;/span&gt;
    &lt;span class=&quot;o&quot;&gt;}&lt;/span&gt;
&lt;/code&gt;&lt;/pre&gt;
&lt;/div&gt;
&lt;ul&gt;
  &lt;li&gt;辅助方法
    &lt;ol&gt;
      &lt;li&gt;检查索引是否合法；&lt;/li&gt;
      &lt;li&gt;返回指定位置的元素；
        &lt;div class=&quot;language-java highlighter-rouge&quot;&gt;&lt;pre class=&quot;highlight&quot;&gt;&lt;code&gt;&lt;span class=&quot;kd&quot;&gt;private&lt;/span&gt; &lt;span class=&quot;kt&quot;&gt;void&lt;/span&gt; &lt;span class=&quot;nf&quot;&gt;rangeCheck&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;(&lt;/span&gt;&lt;span class=&quot;kt&quot;&gt;int&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;index&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;)&lt;/span&gt; &lt;span class=&quot;o&quot;&gt;{&lt;/span&gt;
  &lt;span class=&quot;k&quot;&gt;if&lt;/span&gt; &lt;span class=&quot;o&quot;&gt;(&lt;/span&gt;&lt;span class=&quot;n&quot;&gt;index&lt;/span&gt; &lt;span class=&quot;o&quot;&gt;&amp;gt;=&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;size&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;)&lt;/span&gt;
   &lt;span class=&quot;k&quot;&gt;throw&lt;/span&gt; &lt;span class=&quot;k&quot;&gt;new&lt;/span&gt; &lt;span class=&quot;nf&quot;&gt;IndexOutOfBoundsException&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;(&lt;/span&gt;&lt;span class=&quot;n&quot;&gt;outOfBoundsMsg&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;(&lt;/span&gt;&lt;span class=&quot;n&quot;&gt;index&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;));&lt;/span&gt;
&lt;span class=&quot;o&quot;&gt;}&lt;/span&gt;
&lt;span class=&quot;kd&quot;&gt;private&lt;/span&gt; &lt;span class=&quot;kt&quot;&gt;void&lt;/span&gt; &lt;span class=&quot;nf&quot;&gt;rangeCheckForAdd&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;(&lt;/span&gt;&lt;span class=&quot;kt&quot;&gt;int&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;index&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;)&lt;/span&gt; &lt;span class=&quot;o&quot;&gt;{&lt;/span&gt;
  &lt;span class=&quot;k&quot;&gt;if&lt;/span&gt; &lt;span class=&quot;o&quot;&gt;(&lt;/span&gt;&lt;span class=&quot;n&quot;&gt;index&lt;/span&gt; &lt;span class=&quot;o&quot;&gt;&amp;gt;&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;size&lt;/span&gt; &lt;span class=&quot;o&quot;&gt;||&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;index&lt;/span&gt; &lt;span class=&quot;o&quot;&gt;&amp;lt;&lt;/span&gt; &lt;span class=&quot;mi&quot;&gt;0&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;)&lt;/span&gt;
   &lt;span class=&quot;k&quot;&gt;throw&lt;/span&gt; &lt;span class=&quot;k&quot;&gt;new&lt;/span&gt; &lt;span class=&quot;nf&quot;&gt;IndexOutOfBoundsException&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;(&lt;/span&gt;&lt;span class=&quot;n&quot;&gt;outOfBoundsMsg&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;(&lt;/span&gt;&lt;span class=&quot;n&quot;&gt;index&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;));&lt;/span&gt;
&lt;span class=&quot;o&quot;&gt;}&lt;/span&gt;
&lt;span class=&quot;kd&quot;&gt;private&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;String&lt;/span&gt; &lt;span class=&quot;nf&quot;&gt;outOfBoundsMsg&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;(&lt;/span&gt;&lt;span class=&quot;kt&quot;&gt;int&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;index&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;)&lt;/span&gt; &lt;span class=&quot;o&quot;&gt;{&lt;/span&gt;
  &lt;span class=&quot;k&quot;&gt;return&lt;/span&gt; &lt;span class=&quot;s&quot;&gt;&quot;Index: &quot;&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;+&lt;/span&gt;&lt;span class=&quot;n&quot;&gt;index&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;+&lt;/span&gt;&lt;span class=&quot;s&quot;&gt;&quot;, Size: &quot;&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;+&lt;/span&gt;&lt;span class=&quot;n&quot;&gt;size&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;;&lt;/span&gt;
&lt;span class=&quot;o&quot;&gt;}&lt;/span&gt;
&lt;span class=&quot;c1&quot;&gt;//复用&lt;/span&gt;
&lt;span class=&quot;nd&quot;&gt;@SuppressWarnings&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;(&lt;/span&gt;&lt;span class=&quot;s&quot;&gt;&quot;unchecked&quot;&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;)&lt;/span&gt;
&lt;span class=&quot;n&quot;&gt;E&lt;/span&gt; &lt;span class=&quot;nf&quot;&gt;elementData&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;(&lt;/span&gt;&lt;span class=&quot;kt&quot;&gt;int&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;index&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;)&lt;/span&gt; &lt;span class=&quot;o&quot;&gt;{&lt;/span&gt;
  &lt;span class=&quot;k&quot;&gt;return&lt;/span&gt; &lt;span class=&quot;o&quot;&gt;(&lt;/span&gt;&lt;span class=&quot;n&quot;&gt;E&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;)&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;elementData&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;[&lt;/span&gt;&lt;span class=&quot;n&quot;&gt;index&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;];&lt;/span&gt;
&lt;span class=&quot;o&quot;&gt;}&lt;/span&gt;
&lt;/code&gt;&lt;/pre&gt;
        &lt;/div&gt;
      &lt;/li&gt;
    &lt;/ol&gt;
  &lt;/li&gt;
  &lt;li&gt;SubList与ArrayList的关系
该SubList是非静态内部类实现，基于同一个缓存数组，和Iterator一样维护一个modCount副本，防止并发修改；
    &lt;div class=&quot;language-java highlighter-rouge&quot;&gt;&lt;pre class=&quot;highlight&quot;&gt;&lt;code&gt;&lt;span class=&quot;nd&quot;&gt;@Override&lt;/span&gt;
&lt;span class=&quot;kd&quot;&gt;public&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;List&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;&amp;lt;&lt;/span&gt;&lt;span class=&quot;n&quot;&gt;E&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;&amp;gt;&lt;/span&gt; &lt;span class=&quot;nf&quot;&gt;subList&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;(&lt;/span&gt;&lt;span class=&quot;kt&quot;&gt;int&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;fromIndex&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;,&lt;/span&gt; &lt;span class=&quot;kt&quot;&gt;int&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;toIndex&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;)&lt;/span&gt; &lt;span class=&quot;o&quot;&gt;{&lt;/span&gt;
  &lt;span class=&quot;n&quot;&gt;subListRangeCheck&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;(&lt;/span&gt;&lt;span class=&quot;n&quot;&gt;fromIndex&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;,&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;toIndex&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;,&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;size&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;);&lt;/span&gt;
  &lt;span class=&quot;k&quot;&gt;return&lt;/span&gt; &lt;span class=&quot;k&quot;&gt;new&lt;/span&gt; &lt;span class=&quot;nf&quot;&gt;SubList&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;(&lt;/span&gt;&lt;span class=&quot;k&quot;&gt;this&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;,&lt;/span&gt; &lt;span class=&quot;mi&quot;&gt;0&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;,&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;fromIndex&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;,&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;toIndex&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;);&lt;/span&gt;
&lt;span class=&quot;o&quot;&gt;}&lt;/span&gt;
&lt;/code&gt;&lt;/pre&gt;
    &lt;/div&gt;
    &lt;p&gt;2.6 List实现要点
toArray使用保护性拷贝；总来的来说这一块比较简单；&lt;/p&gt;
    &lt;div class=&quot;language-java highlighter-rouge&quot;&gt;&lt;pre class=&quot;highlight&quot;&gt;&lt;code&gt;&lt;span class=&quot;c1&quot;&gt;//获取指定位置的元素对象引用&lt;/span&gt;
&lt;span class=&quot;nd&quot;&gt;@Override&lt;/span&gt;
&lt;span class=&quot;kd&quot;&gt;public&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;E&lt;/span&gt; &lt;span class=&quot;nf&quot;&gt;get&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;(&lt;/span&gt;&lt;span class=&quot;kt&quot;&gt;int&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;index&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;)&lt;/span&gt; &lt;span class=&quot;o&quot;&gt;{&lt;/span&gt;
  &lt;span class=&quot;n&quot;&gt;rangeCheck&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;(&lt;/span&gt;&lt;span class=&quot;n&quot;&gt;index&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;);&lt;/span&gt;
  &lt;span class=&quot;k&quot;&gt;return&lt;/span&gt; &lt;span class=&quot;nf&quot;&gt;elementData&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;(&lt;/span&gt;&lt;span class=&quot;n&quot;&gt;index&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;);&lt;/span&gt;
&lt;span class=&quot;o&quot;&gt;}&lt;/span&gt;
&lt;span class=&quot;c1&quot;&gt;//注意set方法不是结构性修改，因此并没有modCount++&lt;/span&gt;
&lt;span class=&quot;nd&quot;&gt;@Override&lt;/span&gt;
&lt;span class=&quot;kd&quot;&gt;public&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;E&lt;/span&gt; &lt;span class=&quot;nf&quot;&gt;set&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;(&lt;/span&gt;&lt;span class=&quot;kt&quot;&gt;int&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;index&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;,&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;E&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;element&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;)&lt;/span&gt; &lt;span class=&quot;o&quot;&gt;{&lt;/span&gt;
  &lt;span class=&quot;n&quot;&gt;rangeCheck&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;(&lt;/span&gt;&lt;span class=&quot;n&quot;&gt;index&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;);&lt;/span&gt;
  &lt;span class=&quot;n&quot;&gt;E&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;oldValue&lt;/span&gt; &lt;span class=&quot;o&quot;&gt;=&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;elementData&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;(&lt;/span&gt;&lt;span class=&quot;n&quot;&gt;index&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;);&lt;/span&gt;
  &lt;span class=&quot;n&quot;&gt;elementData&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;[&lt;/span&gt;&lt;span class=&quot;n&quot;&gt;index&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;]&lt;/span&gt; &lt;span class=&quot;o&quot;&gt;=&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;element&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;;&lt;/span&gt;
  &lt;span class=&quot;k&quot;&gt;return&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;oldValue&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;;&lt;/span&gt;
&lt;span class=&quot;o&quot;&gt;}&lt;/span&gt;
&lt;/code&gt;&lt;/pre&gt;
    &lt;/div&gt;
    &lt;p&gt;&lt;em&gt;各种add方法实现&lt;/em&gt;&lt;/p&gt;
    &lt;div class=&quot;language-java highlighter-rouge&quot;&gt;&lt;pre class=&quot;highlight&quot;&gt;&lt;code&gt;&lt;span class=&quot;c1&quot;&gt;//各种add方法实现&lt;/span&gt;
&lt;span class=&quot;nd&quot;&gt;@Override&lt;/span&gt;
&lt;span class=&quot;kd&quot;&gt;public&lt;/span&gt; &lt;span class=&quot;kt&quot;&gt;boolean&lt;/span&gt; &lt;span class=&quot;nf&quot;&gt;add&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;(&lt;/span&gt;&lt;span class=&quot;n&quot;&gt;E&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;e&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;)&lt;/span&gt; &lt;span class=&quot;o&quot;&gt;{&lt;/span&gt;
  &lt;span class=&quot;c1&quot;&gt;//检查并扩增大小，该方法会增加修改计数器，并且一次扩展(3/2)大小防止了频繁扩展带来的开销&lt;/span&gt;
  &lt;span class=&quot;n&quot;&gt;ensureCapacityInternal&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;(&lt;/span&gt;&lt;span class=&quot;n&quot;&gt;size&lt;/span&gt; &lt;span class=&quot;o&quot;&gt;+&lt;/span&gt; &lt;span class=&quot;mi&quot;&gt;1&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;);&lt;/span&gt;
  &lt;span class=&quot;n&quot;&gt;elementData&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;[&lt;/span&gt;&lt;span class=&quot;n&quot;&gt;size&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;++]&lt;/span&gt; &lt;span class=&quot;o&quot;&gt;=&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;e&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;;&lt;/span&gt;
  &lt;span class=&quot;k&quot;&gt;return&lt;/span&gt; &lt;span class=&quot;kc&quot;&gt;true&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;;&lt;/span&gt;
&lt;span class=&quot;o&quot;&gt;}&lt;/span&gt;
&lt;span class=&quot;nd&quot;&gt;@Override&lt;/span&gt;
&lt;span class=&quot;kd&quot;&gt;public&lt;/span&gt; &lt;span class=&quot;kt&quot;&gt;void&lt;/span&gt; &lt;span class=&quot;nf&quot;&gt;add&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;(&lt;/span&gt;&lt;span class=&quot;kt&quot;&gt;int&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;index&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;,&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;E&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;element&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;)&lt;/span&gt; &lt;span class=&quot;o&quot;&gt;{&lt;/span&gt;
  &lt;span class=&quot;n&quot;&gt;rangeCheckForAdd&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;(&lt;/span&gt;&lt;span class=&quot;n&quot;&gt;index&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;);&lt;/span&gt;

  &lt;span class=&quot;n&quot;&gt;ensureCapacityInternal&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;(&lt;/span&gt;&lt;span class=&quot;n&quot;&gt;size&lt;/span&gt; &lt;span class=&quot;o&quot;&gt;+&lt;/span&gt; &lt;span class=&quot;mi&quot;&gt;1&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;);&lt;/span&gt;
  &lt;span class=&quot;c1&quot;&gt;//将数组缓冲区中，index及之后的结点后移&lt;/span&gt;
  &lt;span class=&quot;n&quot;&gt;System&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;.&lt;/span&gt;&lt;span class=&quot;na&quot;&gt;arraycopy&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;(&lt;/span&gt;&lt;span class=&quot;n&quot;&gt;elementData&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;,&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;index&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;,&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;elementData&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;,&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;index&lt;/span&gt; &lt;span class=&quot;o&quot;&gt;+&lt;/span&gt; &lt;span class=&quot;mi&quot;&gt;1&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;,&lt;/span&gt;
          &lt;span class=&quot;n&quot;&gt;size&lt;/span&gt; &lt;span class=&quot;o&quot;&gt;-&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;index&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;);&lt;/span&gt;
  &lt;span class=&quot;n&quot;&gt;elementData&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;[&lt;/span&gt;&lt;span class=&quot;n&quot;&gt;index&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;]&lt;/span&gt; &lt;span class=&quot;o&quot;&gt;=&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;element&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;;&lt;/span&gt;
  &lt;span class=&quot;n&quot;&gt;size&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;++;&lt;/span&gt;
&lt;span class=&quot;o&quot;&gt;}&lt;/span&gt;
&lt;span class=&quot;nd&quot;&gt;@Override&lt;/span&gt;
&lt;span class=&quot;kd&quot;&gt;public&lt;/span&gt; &lt;span class=&quot;kt&quot;&gt;boolean&lt;/span&gt; &lt;span class=&quot;nf&quot;&gt;addAll&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;(&lt;/span&gt;&lt;span class=&quot;n&quot;&gt;Collection&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;&amp;lt;?&lt;/span&gt; &lt;span class=&quot;kd&quot;&gt;extends&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;E&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;&amp;gt;&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;c&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;)&lt;/span&gt; &lt;span class=&quot;o&quot;&gt;{&lt;/span&gt;
  &lt;span class=&quot;c1&quot;&gt;//获取集合中的元素数组，这样做的好处在于可以自由操作这些元素，而不用影响集合c&lt;/span&gt;
  &lt;span class=&quot;n&quot;&gt;Object&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;[]&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;a&lt;/span&gt; &lt;span class=&quot;o&quot;&gt;=&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;c&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;.&lt;/span&gt;&lt;span class=&quot;na&quot;&gt;toArray&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;();&lt;/span&gt;
  &lt;span class=&quot;kt&quot;&gt;int&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;numNew&lt;/span&gt; &lt;span class=&quot;o&quot;&gt;=&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;a&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;.&lt;/span&gt;&lt;span class=&quot;na&quot;&gt;length&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;;&lt;/span&gt;
  &lt;span class=&quot;n&quot;&gt;ensureCapacityInternal&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;(&lt;/span&gt;&lt;span class=&quot;n&quot;&gt;size&lt;/span&gt; &lt;span class=&quot;o&quot;&gt;+&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;numNew&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;);&lt;/span&gt; &lt;span class=&quot;c1&quot;&gt;//增加modCount&lt;/span&gt;
  &lt;span class=&quot;n&quot;&gt;System&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;.&lt;/span&gt;&lt;span class=&quot;na&quot;&gt;arraycopy&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;(&lt;/span&gt;&lt;span class=&quot;n&quot;&gt;a&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;,&lt;/span&gt; &lt;span class=&quot;mi&quot;&gt;0&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;,&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;elementData&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;,&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;size&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;,&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;numNew&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;);&lt;/span&gt;
  &lt;span class=&quot;n&quot;&gt;size&lt;/span&gt; &lt;span class=&quot;o&quot;&gt;+=&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;numNew&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;;&lt;/span&gt;
  &lt;span class=&quot;k&quot;&gt;return&lt;/span&gt; &lt;span class=&quot;kc&quot;&gt;true&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;;&lt;/span&gt;
&lt;span class=&quot;o&quot;&gt;}&lt;/span&gt;
&lt;span class=&quot;nd&quot;&gt;@Override&lt;/span&gt;
&lt;span class=&quot;kd&quot;&gt;public&lt;/span&gt; &lt;span class=&quot;kt&quot;&gt;boolean&lt;/span&gt; &lt;span class=&quot;nf&quot;&gt;addAll&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;(&lt;/span&gt;&lt;span class=&quot;kt&quot;&gt;int&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;index&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;,&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;Collection&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;&amp;lt;?&lt;/span&gt; &lt;span class=&quot;kd&quot;&gt;extends&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;E&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;&amp;gt;&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;c&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;)&lt;/span&gt; &lt;span class=&quot;o&quot;&gt;{&lt;/span&gt;
  &lt;span class=&quot;n&quot;&gt;rangeCheckForAdd&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;(&lt;/span&gt;&lt;span class=&quot;n&quot;&gt;index&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;);&lt;/span&gt;

  &lt;span class=&quot;n&quot;&gt;Object&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;[]&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;a&lt;/span&gt; &lt;span class=&quot;o&quot;&gt;=&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;c&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;.&lt;/span&gt;&lt;span class=&quot;na&quot;&gt;toArray&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;();&lt;/span&gt;
  &lt;span class=&quot;kt&quot;&gt;int&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;numNew&lt;/span&gt; &lt;span class=&quot;o&quot;&gt;=&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;a&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;.&lt;/span&gt;&lt;span class=&quot;na&quot;&gt;length&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;;&lt;/span&gt;
  &lt;span class=&quot;n&quot;&gt;ensureCapacityInternal&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;(&lt;/span&gt;&lt;span class=&quot;n&quot;&gt;size&lt;/span&gt; &lt;span class=&quot;o&quot;&gt;+&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;numNew&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;);&lt;/span&gt; &lt;span class=&quot;c1&quot;&gt;//增加modCount&lt;/span&gt;

  &lt;span class=&quot;c1&quot;&gt;//如果是在尾部插入就不需要移动了&lt;/span&gt;
  &lt;span class=&quot;kt&quot;&gt;int&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;numMoved&lt;/span&gt; &lt;span class=&quot;o&quot;&gt;=&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;size&lt;/span&gt; &lt;span class=&quot;o&quot;&gt;-&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;index&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;;&lt;/span&gt;
  &lt;span class=&quot;k&quot;&gt;if&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;(&lt;/span&gt;&lt;span class=&quot;n&quot;&gt;numMoved&lt;/span&gt; &lt;span class=&quot;o&quot;&gt;&amp;gt;&lt;/span&gt; &lt;span class=&quot;mi&quot;&gt;0&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;)&lt;/span&gt;
      &lt;span class=&quot;n&quot;&gt;System&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;.&lt;/span&gt;&lt;span class=&quot;na&quot;&gt;arraycopy&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;(&lt;/span&gt;&lt;span class=&quot;n&quot;&gt;elementData&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;,&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;index&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;,&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;elementData&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;,&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;index&lt;/span&gt; &lt;span class=&quot;o&quot;&gt;+&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;numNew&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;,&lt;/span&gt;
              &lt;span class=&quot;n&quot;&gt;numMoved&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;);&lt;/span&gt;

  &lt;span class=&quot;n&quot;&gt;System&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;.&lt;/span&gt;&lt;span class=&quot;na&quot;&gt;arraycopy&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;(&lt;/span&gt;&lt;span class=&quot;n&quot;&gt;a&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;,&lt;/span&gt; &lt;span class=&quot;mi&quot;&gt;0&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;,&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;elementData&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;,&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;index&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;,&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;numNew&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;);&lt;/span&gt;
  &lt;span class=&quot;n&quot;&gt;size&lt;/span&gt; &lt;span class=&quot;o&quot;&gt;+=&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;numNew&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;;&lt;/span&gt;
  &lt;span class=&quot;k&quot;&gt;return&lt;/span&gt; &lt;span class=&quot;kc&quot;&gt;true&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;;&lt;/span&gt;
&lt;span class=&quot;o&quot;&gt;}&lt;/span&gt;
&lt;/code&gt;&lt;/pre&gt;
    &lt;/div&gt;
    &lt;p&gt;&lt;em&gt;各种删除的实现&lt;/em&gt;&lt;/p&gt;
    &lt;div class=&quot;language-java highlighter-rouge&quot;&gt;&lt;pre class=&quot;highlight&quot;&gt;&lt;code&gt;&lt;span class=&quot;c1&quot;&gt;//各种删除的实现&lt;/span&gt;
&lt;span class=&quot;nd&quot;&gt;@Override&lt;/span&gt;
&lt;span class=&quot;kd&quot;&gt;public&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;E&lt;/span&gt; &lt;span class=&quot;nf&quot;&gt;remove&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;(&lt;/span&gt;&lt;span class=&quot;kt&quot;&gt;int&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;index&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;)&lt;/span&gt; &lt;span class=&quot;o&quot;&gt;{&lt;/span&gt;
  &lt;span class=&quot;n&quot;&gt;rangeCheck&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;(&lt;/span&gt;&lt;span class=&quot;n&quot;&gt;index&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;);&lt;/span&gt;

  &lt;span class=&quot;n&quot;&gt;modCount&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;++;&lt;/span&gt; &lt;span class=&quot;c1&quot;&gt;//fail-fast&lt;/span&gt;
  &lt;span class=&quot;n&quot;&gt;E&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;oldValue&lt;/span&gt; &lt;span class=&quot;o&quot;&gt;=&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;elementData&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;(&lt;/span&gt;&lt;span class=&quot;n&quot;&gt;index&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;);&lt;/span&gt;

  &lt;span class=&quot;kt&quot;&gt;int&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;numMoved&lt;/span&gt; &lt;span class=&quot;o&quot;&gt;=&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;size&lt;/span&gt; &lt;span class=&quot;o&quot;&gt;-&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;index&lt;/span&gt; &lt;span class=&quot;o&quot;&gt;-&lt;/span&gt; &lt;span class=&quot;mi&quot;&gt;1&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;;&lt;/span&gt;
  &lt;span class=&quot;k&quot;&gt;if&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;(&lt;/span&gt;&lt;span class=&quot;n&quot;&gt;numMoved&lt;/span&gt; &lt;span class=&quot;o&quot;&gt;&amp;gt;&lt;/span&gt; &lt;span class=&quot;mi&quot;&gt;0&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;)&lt;/span&gt;
      &lt;span class=&quot;n&quot;&gt;System&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;.&lt;/span&gt;&lt;span class=&quot;na&quot;&gt;arraycopy&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;(&lt;/span&gt;&lt;span class=&quot;n&quot;&gt;elementData&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;,&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;index&lt;/span&gt; &lt;span class=&quot;o&quot;&gt;+&lt;/span&gt; &lt;span class=&quot;mi&quot;&gt;1&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;,&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;elementData&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;,&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;index&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;,&lt;/span&gt;
              &lt;span class=&quot;n&quot;&gt;numMoved&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;);&lt;/span&gt;
  &lt;span class=&quot;n&quot;&gt;elementData&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;[--&lt;/span&gt;&lt;span class=&quot;n&quot;&gt;size&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;]&lt;/span&gt; &lt;span class=&quot;o&quot;&gt;=&lt;/span&gt; &lt;span class=&quot;kc&quot;&gt;null&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;;&lt;/span&gt; &lt;span class=&quot;c1&quot;&gt;//防止内存泄漏&lt;/span&gt;

  &lt;span class=&quot;k&quot;&gt;return&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;oldValue&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;;&lt;/span&gt;
&lt;span class=&quot;o&quot;&gt;}&lt;/span&gt;
&lt;span class=&quot;nd&quot;&gt;@Override&lt;/span&gt;
&lt;span class=&quot;kd&quot;&gt;public&lt;/span&gt; &lt;span class=&quot;kt&quot;&gt;boolean&lt;/span&gt; &lt;span class=&quot;nf&quot;&gt;remove&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;(&lt;/span&gt;&lt;span class=&quot;n&quot;&gt;Object&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;o&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;)&lt;/span&gt; &lt;span class=&quot;o&quot;&gt;{&lt;/span&gt;
  &lt;span class=&quot;k&quot;&gt;if&lt;/span&gt; &lt;span class=&quot;o&quot;&gt;(&lt;/span&gt;&lt;span class=&quot;n&quot;&gt;o&lt;/span&gt; &lt;span class=&quot;o&quot;&gt;==&lt;/span&gt; &lt;span class=&quot;kc&quot;&gt;null&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;)&lt;/span&gt; &lt;span class=&quot;o&quot;&gt;{&lt;/span&gt;
      &lt;span class=&quot;k&quot;&gt;for&lt;/span&gt; &lt;span class=&quot;o&quot;&gt;(&lt;/span&gt;&lt;span class=&quot;kt&quot;&gt;int&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;index&lt;/span&gt; &lt;span class=&quot;o&quot;&gt;=&lt;/span&gt; &lt;span class=&quot;mi&quot;&gt;0&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;;&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;index&lt;/span&gt; &lt;span class=&quot;o&quot;&gt;&amp;lt;&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;size&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;;&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;index&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;++)&lt;/span&gt;
          &lt;span class=&quot;k&quot;&gt;if&lt;/span&gt; &lt;span class=&quot;o&quot;&gt;(&lt;/span&gt;&lt;span class=&quot;n&quot;&gt;elementData&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;[&lt;/span&gt;&lt;span class=&quot;n&quot;&gt;index&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;]&lt;/span&gt; &lt;span class=&quot;o&quot;&gt;==&lt;/span&gt; &lt;span class=&quot;kc&quot;&gt;null&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;)&lt;/span&gt; &lt;span class=&quot;o&quot;&gt;{&lt;/span&gt;
              &lt;span class=&quot;n&quot;&gt;fastRemove&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;(&lt;/span&gt;&lt;span class=&quot;n&quot;&gt;index&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;);&lt;/span&gt;
              &lt;span class=&quot;k&quot;&gt;return&lt;/span&gt; &lt;span class=&quot;kc&quot;&gt;true&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;;&lt;/span&gt;
          &lt;span class=&quot;o&quot;&gt;}&lt;/span&gt;
  &lt;span class=&quot;o&quot;&gt;}&lt;/span&gt; &lt;span class=&quot;k&quot;&gt;else&lt;/span&gt; &lt;span class=&quot;o&quot;&gt;{&lt;/span&gt;
      &lt;span class=&quot;k&quot;&gt;for&lt;/span&gt; &lt;span class=&quot;o&quot;&gt;(&lt;/span&gt;&lt;span class=&quot;kt&quot;&gt;int&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;index&lt;/span&gt; &lt;span class=&quot;o&quot;&gt;=&lt;/span&gt; &lt;span class=&quot;mi&quot;&gt;0&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;;&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;index&lt;/span&gt; &lt;span class=&quot;o&quot;&gt;&amp;lt;&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;size&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;;&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;index&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;++)&lt;/span&gt;
          &lt;span class=&quot;k&quot;&gt;if&lt;/span&gt; &lt;span class=&quot;o&quot;&gt;(&lt;/span&gt;&lt;span class=&quot;n&quot;&gt;o&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;.&lt;/span&gt;&lt;span class=&quot;na&quot;&gt;equals&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;(&lt;/span&gt;&lt;span class=&quot;n&quot;&gt;elementData&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;[&lt;/span&gt;&lt;span class=&quot;n&quot;&gt;index&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;]))&lt;/span&gt; &lt;span class=&quot;o&quot;&gt;{&lt;/span&gt;
              &lt;span class=&quot;n&quot;&gt;fastRemove&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;(&lt;/span&gt;&lt;span class=&quot;n&quot;&gt;index&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;);&lt;/span&gt;
              &lt;span class=&quot;k&quot;&gt;return&lt;/span&gt; &lt;span class=&quot;kc&quot;&gt;true&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;;&lt;/span&gt;
          &lt;span class=&quot;o&quot;&gt;}&lt;/span&gt;
  &lt;span class=&quot;o&quot;&gt;}&lt;/span&gt;
  &lt;span class=&quot;k&quot;&gt;return&lt;/span&gt; &lt;span class=&quot;kc&quot;&gt;false&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;;&lt;/span&gt;
&lt;span class=&quot;o&quot;&gt;}&lt;/span&gt;
&lt;span class=&quot;c1&quot;&gt;//保留差集&lt;/span&gt;
&lt;span class=&quot;nd&quot;&gt;@Override&lt;/span&gt;
&lt;span class=&quot;kd&quot;&gt;public&lt;/span&gt; &lt;span class=&quot;kt&quot;&gt;boolean&lt;/span&gt; &lt;span class=&quot;nf&quot;&gt;removeAll&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;(&lt;/span&gt;&lt;span class=&quot;n&quot;&gt;Collection&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;&amp;lt;?&amp;gt;&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;c&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;)&lt;/span&gt; &lt;span class=&quot;o&quot;&gt;{&lt;/span&gt;
  &lt;span class=&quot;n&quot;&gt;Objects&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;.&lt;/span&gt;&lt;span class=&quot;na&quot;&gt;nonNull&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;(&lt;/span&gt;&lt;span class=&quot;n&quot;&gt;c&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;);&lt;/span&gt;
  &lt;span class=&quot;k&quot;&gt;return&lt;/span&gt; &lt;span class=&quot;nf&quot;&gt;batchRemove&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;(&lt;/span&gt;&lt;span class=&quot;n&quot;&gt;c&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;,&lt;/span&gt; &lt;span class=&quot;kc&quot;&gt;false&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;);&lt;/span&gt;
&lt;span class=&quot;o&quot;&gt;}&lt;/span&gt;
&lt;/code&gt;&lt;/pre&gt;
    &lt;/div&gt;
    &lt;div class=&quot;language-java highlighter-rouge&quot;&gt;&lt;pre class=&quot;highlight&quot;&gt;&lt;code&gt;&lt;span class=&quot;c1&quot;&gt;//保留交集&lt;/span&gt;
&lt;span class=&quot;nd&quot;&gt;@Override&lt;/span&gt;
&lt;span class=&quot;kd&quot;&gt;public&lt;/span&gt; &lt;span class=&quot;kt&quot;&gt;boolean&lt;/span&gt; &lt;span class=&quot;nf&quot;&gt;retainAll&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;(&lt;/span&gt;&lt;span class=&quot;n&quot;&gt;Collection&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;&amp;lt;?&amp;gt;&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;c&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;)&lt;/span&gt; &lt;span class=&quot;o&quot;&gt;{&lt;/span&gt;
  &lt;span class=&quot;n&quot;&gt;Objects&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;.&lt;/span&gt;&lt;span class=&quot;na&quot;&gt;nonNull&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;(&lt;/span&gt;&lt;span class=&quot;n&quot;&gt;c&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;);&lt;/span&gt;
  &lt;span class=&quot;k&quot;&gt;return&lt;/span&gt; &lt;span class=&quot;nf&quot;&gt;batchRemove&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;(&lt;/span&gt;&lt;span class=&quot;n&quot;&gt;c&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;,&lt;/span&gt; &lt;span class=&quot;kc&quot;&gt;true&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;);&lt;/span&gt;
&lt;span class=&quot;o&quot;&gt;}&lt;/span&gt;
&lt;span class=&quot;c1&quot;&gt;//置空防止内存泄漏&lt;/span&gt;
&lt;span class=&quot;nd&quot;&gt;@Override&lt;/span&gt;
&lt;span class=&quot;kd&quot;&gt;public&lt;/span&gt; &lt;span class=&quot;kt&quot;&gt;void&lt;/span&gt; &lt;span class=&quot;nf&quot;&gt;clear&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;()&lt;/span&gt; &lt;span class=&quot;o&quot;&gt;{&lt;/span&gt;
  &lt;span class=&quot;n&quot;&gt;modCount&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;++;&lt;/span&gt;

  &lt;span class=&quot;k&quot;&gt;for&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;(&lt;/span&gt;&lt;span class=&quot;kt&quot;&gt;int&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;i&lt;/span&gt; &lt;span class=&quot;o&quot;&gt;=&lt;/span&gt; &lt;span class=&quot;mi&quot;&gt;0&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;;&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;i&lt;/span&gt; &lt;span class=&quot;o&quot;&gt;&amp;lt;&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;size&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;;&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;i&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;++)&lt;/span&gt;
      &lt;span class=&quot;n&quot;&gt;elementData&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;[&lt;/span&gt;&lt;span class=&quot;n&quot;&gt;i&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;]&lt;/span&gt; &lt;span class=&quot;o&quot;&gt;=&lt;/span&gt; &lt;span class=&quot;kc&quot;&gt;null&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;;&lt;/span&gt;

  &lt;span class=&quot;n&quot;&gt;size&lt;/span&gt; &lt;span class=&quot;o&quot;&gt;=&lt;/span&gt; &lt;span class=&quot;mi&quot;&gt;0&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;;&lt;/span&gt;
&lt;span class=&quot;o&quot;&gt;}&lt;/span&gt;
&lt;span class=&quot;c1&quot;&gt;//正向查找，返回元素第一次出现的索引值&lt;/span&gt;
&lt;span class=&quot;nd&quot;&gt;@Override&lt;/span&gt;
&lt;span class=&quot;kd&quot;&gt;public&lt;/span&gt; &lt;span class=&quot;kt&quot;&gt;int&lt;/span&gt; &lt;span class=&quot;nf&quot;&gt;indexOf&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;(&lt;/span&gt;&lt;span class=&quot;n&quot;&gt;Object&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;o&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;)&lt;/span&gt; &lt;span class=&quot;o&quot;&gt;{&lt;/span&gt;
  &lt;span class=&quot;k&quot;&gt;if&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;(&lt;/span&gt;&lt;span class=&quot;n&quot;&gt;o&lt;/span&gt; &lt;span class=&quot;o&quot;&gt;==&lt;/span&gt; &lt;span class=&quot;kc&quot;&gt;null&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;)&lt;/span&gt; &lt;span class=&quot;o&quot;&gt;{&lt;/span&gt;
      &lt;span class=&quot;k&quot;&gt;for&lt;/span&gt; &lt;span class=&quot;o&quot;&gt;(&lt;/span&gt;&lt;span class=&quot;kt&quot;&gt;int&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;i&lt;/span&gt; &lt;span class=&quot;o&quot;&gt;=&lt;/span&gt; &lt;span class=&quot;mi&quot;&gt;0&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;;&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;i&lt;/span&gt; &lt;span class=&quot;o&quot;&gt;&amp;lt;&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;size&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;;&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;i&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;++)&lt;/span&gt;
          &lt;span class=&quot;k&quot;&gt;if&lt;/span&gt; &lt;span class=&quot;o&quot;&gt;(&lt;/span&gt;&lt;span class=&quot;n&quot;&gt;elementData&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;[&lt;/span&gt;&lt;span class=&quot;n&quot;&gt;i&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;]&lt;/span&gt; &lt;span class=&quot;o&quot;&gt;==&lt;/span&gt; &lt;span class=&quot;kc&quot;&gt;null&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;)&lt;/span&gt;
              &lt;span class=&quot;k&quot;&gt;return&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;i&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;;&lt;/span&gt;
  &lt;span class=&quot;o&quot;&gt;}&lt;/span&gt; &lt;span class=&quot;k&quot;&gt;else&lt;/span&gt; &lt;span class=&quot;o&quot;&gt;{&lt;/span&gt;
      &lt;span class=&quot;k&quot;&gt;for&lt;/span&gt; &lt;span class=&quot;o&quot;&gt;(&lt;/span&gt;&lt;span class=&quot;kt&quot;&gt;int&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;i&lt;/span&gt; &lt;span class=&quot;o&quot;&gt;=&lt;/span&gt; &lt;span class=&quot;mi&quot;&gt;0&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;;&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;i&lt;/span&gt; &lt;span class=&quot;o&quot;&gt;&amp;lt;&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;size&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;;&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;i&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;++)&lt;/span&gt;
          &lt;span class=&quot;k&quot;&gt;if&lt;/span&gt; &lt;span class=&quot;o&quot;&gt;(&lt;/span&gt;&lt;span class=&quot;n&quot;&gt;o&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;.&lt;/span&gt;&lt;span class=&quot;na&quot;&gt;equals&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;(&lt;/span&gt;&lt;span class=&quot;n&quot;&gt;elementData&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;[&lt;/span&gt;&lt;span class=&quot;n&quot;&gt;i&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;]))&lt;/span&gt;
              &lt;span class=&quot;k&quot;&gt;return&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;i&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;;&lt;/span&gt;
  &lt;span class=&quot;o&quot;&gt;}&lt;/span&gt;
  &lt;span class=&quot;k&quot;&gt;return&lt;/span&gt; &lt;span class=&quot;o&quot;&gt;-&lt;/span&gt;&lt;span class=&quot;mi&quot;&gt;1&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;;&lt;/span&gt;
&lt;span class=&quot;o&quot;&gt;}&lt;/span&gt;
&lt;span class=&quot;c1&quot;&gt;//反向查找，返回元素最后一次出现的索引值&lt;/span&gt;
&lt;span class=&quot;nd&quot;&gt;@Override&lt;/span&gt;
&lt;span class=&quot;kd&quot;&gt;public&lt;/span&gt; &lt;span class=&quot;kt&quot;&gt;int&lt;/span&gt; &lt;span class=&quot;nf&quot;&gt;lastIndexOf&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;(&lt;/span&gt;&lt;span class=&quot;n&quot;&gt;Object&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;o&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;)&lt;/span&gt; &lt;span class=&quot;o&quot;&gt;{&lt;/span&gt;
  &lt;span class=&quot;k&quot;&gt;if&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;(&lt;/span&gt;&lt;span class=&quot;n&quot;&gt;o&lt;/span&gt; &lt;span class=&quot;o&quot;&gt;==&lt;/span&gt; &lt;span class=&quot;kc&quot;&gt;null&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;)&lt;/span&gt; &lt;span class=&quot;o&quot;&gt;{&lt;/span&gt;
      &lt;span class=&quot;k&quot;&gt;for&lt;/span&gt; &lt;span class=&quot;o&quot;&gt;(&lt;/span&gt;&lt;span class=&quot;kt&quot;&gt;int&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;i&lt;/span&gt; &lt;span class=&quot;o&quot;&gt;=&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;size&lt;/span&gt; &lt;span class=&quot;o&quot;&gt;-&lt;/span&gt; &lt;span class=&quot;mi&quot;&gt;1&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;;&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;i&lt;/span&gt; &lt;span class=&quot;o&quot;&gt;&amp;gt;=&lt;/span&gt; &lt;span class=&quot;mi&quot;&gt;0&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;;&lt;/span&gt; &lt;span class=&quot;o&quot;&gt;--&lt;/span&gt;&lt;span class=&quot;n&quot;&gt;i&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;)&lt;/span&gt;
          &lt;span class=&quot;k&quot;&gt;if&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;(&lt;/span&gt;&lt;span class=&quot;n&quot;&gt;elementData&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;[&lt;/span&gt;&lt;span class=&quot;n&quot;&gt;i&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;]&lt;/span&gt; &lt;span class=&quot;o&quot;&gt;==&lt;/span&gt; &lt;span class=&quot;kc&quot;&gt;null&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;)&lt;/span&gt;
              &lt;span class=&quot;k&quot;&gt;return&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;i&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;;&lt;/span&gt;
  &lt;span class=&quot;o&quot;&gt;}&lt;/span&gt; &lt;span class=&quot;k&quot;&gt;else&lt;/span&gt; &lt;span class=&quot;o&quot;&gt;{&lt;/span&gt;
      &lt;span class=&quot;k&quot;&gt;for&lt;/span&gt; &lt;span class=&quot;o&quot;&gt;(&lt;/span&gt;&lt;span class=&quot;kt&quot;&gt;int&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;i&lt;/span&gt; &lt;span class=&quot;o&quot;&gt;=&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;size&lt;/span&gt; &lt;span class=&quot;o&quot;&gt;-&lt;/span&gt; &lt;span class=&quot;mi&quot;&gt;1&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;;&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;i&lt;/span&gt; &lt;span class=&quot;o&quot;&gt;&amp;gt;=&lt;/span&gt; &lt;span class=&quot;mi&quot;&gt;0&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;;&lt;/span&gt; &lt;span class=&quot;o&quot;&gt;--&lt;/span&gt;&lt;span class=&quot;n&quot;&gt;i&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;)&lt;/span&gt;
          &lt;span class=&quot;k&quot;&gt;if&lt;/span&gt; &lt;span class=&quot;o&quot;&gt;(&lt;/span&gt;&lt;span class=&quot;n&quot;&gt;o&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;.&lt;/span&gt;&lt;span class=&quot;na&quot;&gt;equals&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;(&lt;/span&gt;&lt;span class=&quot;n&quot;&gt;elementData&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;[&lt;/span&gt;&lt;span class=&quot;n&quot;&gt;i&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;]))&lt;/span&gt;
              &lt;span class=&quot;k&quot;&gt;return&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;i&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;;&lt;/span&gt;
  &lt;span class=&quot;o&quot;&gt;}&lt;/span&gt;
  &lt;span class=&quot;k&quot;&gt;return&lt;/span&gt; &lt;span class=&quot;o&quot;&gt;-&lt;/span&gt;&lt;span class=&quot;mi&quot;&gt;1&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;;&lt;/span&gt;
&lt;span class=&quot;o&quot;&gt;}&lt;/span&gt;
&lt;span class=&quot;nd&quot;&gt;@Override&lt;/span&gt;
&lt;span class=&quot;kd&quot;&gt;public&lt;/span&gt; &lt;span class=&quot;kt&quot;&gt;boolean&lt;/span&gt; &lt;span class=&quot;nf&quot;&gt;contains&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;(&lt;/span&gt;&lt;span class=&quot;n&quot;&gt;Object&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;o&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;)&lt;/span&gt; &lt;span class=&quot;o&quot;&gt;{&lt;/span&gt;
  &lt;span class=&quot;k&quot;&gt;return&lt;/span&gt; &lt;span class=&quot;nf&quot;&gt;indexOf&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;(&lt;/span&gt;&lt;span class=&quot;n&quot;&gt;o&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;)&lt;/span&gt; &lt;span class=&quot;o&quot;&gt;&amp;gt;=&lt;/span&gt; &lt;span class=&quot;mi&quot;&gt;0&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;;&lt;/span&gt;
&lt;span class=&quot;o&quot;&gt;}&lt;/span&gt;
&lt;span class=&quot;c1&quot;&gt;//对数组进行排序&lt;/span&gt;
&lt;span class=&quot;nd&quot;&gt;@Override&lt;/span&gt;
&lt;span class=&quot;nd&quot;&gt;@SuppressWarnings&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;(&lt;/span&gt;&lt;span class=&quot;s&quot;&gt;&quot;unchecked&quot;&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;)&lt;/span&gt;
&lt;span class=&quot;kd&quot;&gt;public&lt;/span&gt; &lt;span class=&quot;kt&quot;&gt;void&lt;/span&gt; &lt;span class=&quot;nf&quot;&gt;sort&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;(&lt;/span&gt;&lt;span class=&quot;n&quot;&gt;Comparator&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;&amp;lt;?&lt;/span&gt; &lt;span class=&quot;kd&quot;&gt;super&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;E&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;&amp;gt;&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;c&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;)&lt;/span&gt; &lt;span class=&quot;o&quot;&gt;{&lt;/span&gt;
  &lt;span class=&quot;kd&quot;&gt;final&lt;/span&gt; &lt;span class=&quot;kt&quot;&gt;int&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;expectedModCount&lt;/span&gt; &lt;span class=&quot;o&quot;&gt;=&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;modCount&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;;&lt;/span&gt;
  &lt;span class=&quot;n&quot;&gt;Arrays&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;.&lt;/span&gt;&lt;span class=&quot;na&quot;&gt;sort&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;((&lt;/span&gt;&lt;span class=&quot;n&quot;&gt;E&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;[])&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;elementData&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;,&lt;/span&gt; &lt;span class=&quot;mi&quot;&gt;0&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;,&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;size&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;,&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;c&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;);&lt;/span&gt;
  &lt;span class=&quot;k&quot;&gt;if&lt;/span&gt; &lt;span class=&quot;o&quot;&gt;(&lt;/span&gt;&lt;span class=&quot;n&quot;&gt;modCount&lt;/span&gt; &lt;span class=&quot;o&quot;&gt;!=&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;expectedModCount&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;)&lt;/span&gt; &lt;span class=&quot;o&quot;&gt;{&lt;/span&gt;
      &lt;span class=&quot;k&quot;&gt;throw&lt;/span&gt; &lt;span class=&quot;k&quot;&gt;new&lt;/span&gt; &lt;span class=&quot;nf&quot;&gt;ConcurrentModificationException&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;();&lt;/span&gt;
  &lt;span class=&quot;o&quot;&gt;}&lt;/span&gt;
  &lt;span class=&quot;n&quot;&gt;modCount&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;++;&lt;/span&gt;
&lt;span class=&quot;o&quot;&gt;}&lt;/span&gt;
&lt;span class=&quot;c1&quot;&gt;//保护性拷贝&lt;/span&gt;
&lt;span class=&quot;nd&quot;&gt;@Override&lt;/span&gt;
&lt;span class=&quot;kd&quot;&gt;public&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;Object&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;[]&lt;/span&gt; &lt;span class=&quot;nf&quot;&gt;toArray&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;()&lt;/span&gt; &lt;span class=&quot;o&quot;&gt;{&lt;/span&gt;
  &lt;span class=&quot;k&quot;&gt;return&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;Arrays&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;.&lt;/span&gt;&lt;span class=&quot;na&quot;&gt;copyOf&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;(&lt;/span&gt;&lt;span class=&quot;n&quot;&gt;elementData&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;,&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;size&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;);&lt;/span&gt;
&lt;span class=&quot;o&quot;&gt;}&lt;/span&gt;
&lt;span class=&quot;nd&quot;&gt;@SuppressWarnings&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;(&lt;/span&gt;&lt;span class=&quot;s&quot;&gt;&quot;unchecked&quot;&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;)&lt;/span&gt;
&lt;span class=&quot;nd&quot;&gt;@Override&lt;/span&gt;
&lt;span class=&quot;kd&quot;&gt;public&lt;/span&gt; &lt;span class=&quot;o&quot;&gt;&amp;lt;&lt;/span&gt;&lt;span class=&quot;n&quot;&gt;T&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;&amp;gt;&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;T&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;[]&lt;/span&gt; &lt;span class=&quot;nf&quot;&gt;toArray&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;(&lt;/span&gt;&lt;span class=&quot;n&quot;&gt;T&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;[]&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;a&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;)&lt;/span&gt; &lt;span class=&quot;o&quot;&gt;{&lt;/span&gt;
  &lt;span class=&quot;k&quot;&gt;if&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;(&lt;/span&gt;&lt;span class=&quot;n&quot;&gt;a&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;.&lt;/span&gt;&lt;span class=&quot;na&quot;&gt;length&lt;/span&gt; &lt;span class=&quot;o&quot;&gt;&amp;lt;&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;size&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;)&lt;/span&gt;
      &lt;span class=&quot;c1&quot;&gt;//必须创建一个与参数类型相同的数组&lt;/span&gt;
      &lt;span class=&quot;k&quot;&gt;return&lt;/span&gt; &lt;span class=&quot;o&quot;&gt;(&lt;/span&gt;&lt;span class=&quot;n&quot;&gt;T&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;[])&lt;/span&gt;&lt;span class=&quot;n&quot;&gt;Arrays&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;.&lt;/span&gt;&lt;span class=&quot;na&quot;&gt;copyOf&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;(&lt;/span&gt;&lt;span class=&quot;n&quot;&gt;elementData&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;,&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;size&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;,&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;a&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;.&lt;/span&gt;&lt;span class=&quot;na&quot;&gt;getClass&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;());&lt;/span&gt;
  &lt;span class=&quot;n&quot;&gt;System&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;.&lt;/span&gt;&lt;span class=&quot;na&quot;&gt;arraycopy&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;(&lt;/span&gt;&lt;span class=&quot;n&quot;&gt;elementData&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;,&lt;/span&gt; &lt;span class=&quot;mi&quot;&gt;0&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;,&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;a&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;,&lt;/span&gt; &lt;span class=&quot;mi&quot;&gt;0&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;,&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;size&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;);&lt;/span&gt;
  &lt;span class=&quot;k&quot;&gt;if&lt;/span&gt; &lt;span class=&quot;o&quot;&gt;(&lt;/span&gt;&lt;span class=&quot;n&quot;&gt;a&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;.&lt;/span&gt;&lt;span class=&quot;na&quot;&gt;length&lt;/span&gt; &lt;span class=&quot;o&quot;&gt;&amp;gt;&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;size&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;)&lt;/span&gt;
      &lt;span class=&quot;n&quot;&gt;a&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;[&lt;/span&gt;&lt;span class=&quot;n&quot;&gt;size&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;]&lt;/span&gt; &lt;span class=&quot;o&quot;&gt;=&lt;/span&gt; &lt;span class=&quot;kc&quot;&gt;null&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;;&lt;/span&gt; &lt;span class=&quot;c1&quot;&gt;//用来帮助调用者确定集合长度（只有在明确知道集合中没有null元素时才有用）&lt;/span&gt;
  &lt;span class=&quot;k&quot;&gt;return&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;a&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;;&lt;/span&gt;
&lt;span class=&quot;o&quot;&gt;}&lt;/span&gt;
&lt;/code&gt;&lt;/pre&gt;
    &lt;/div&gt;
  &lt;/li&gt;
&lt;/ul&gt;

&lt;p&gt;&lt;strong&gt;Arraylist排序方面还没有看。&lt;/strong&gt;&lt;/p&gt;</content><category term="JavaBasic" /><summary type="html">ArrayList源码分析.</summary></entry></feed>