aula20.java

/*class Node{
    Node next;
    Node prev;
    int data;

    Node(int value){
        data = value;
        next = null;
        prev = null;
    }
}
class Stack{
    private Node head;
    private Node tail;

    Stack()
    {
        head = null;
        tail = null;
    }
    public void push(int value)
    {
        Node newNode = new Node(value);
        if(head == null)
        {
            head = newNode;
            head.next = null;
            head.prev = null;
            tail = newNode;
        }
        else
        {
            newNode.prev = tail;
            tail.next = newNode;
            tail = newNode;
        }
    }

    public void pop()
    {
        if(head == null)
            System.out.println("stack underflow");

        if(head == tail)
        {
            head = null;
            tail = null;
        }
        else
        {
            Node n = tail;
            tail = tail.prev;
            n.prev = null;
            tail.next = null;
        }
    }

    public void merge(Stack s)
    {
        if(s.tail != null)
        {
            head.prev = s.tail;
            s.tail.next = head;    
        }
        
        head = s.head;
        s.tail = null;
        s.head = null;
    }

    public void display()
    {
        if(tail != null)
        {
            Node n = tail;
            while(n != null)
            {
                System.out.print(n.data + " ");
                n = n.prev;
            }
            System.out.println();
        }
        else
        {
            System.out.println("Stack Underflow");
        }
    }
}
class aula20{
    public static void main(String[] args)
    {
        Stack ms1 = new Stack();
        Stack ms2 = new Stack();

        ms1.push(6);
        ms1.push(5);
        ms1.push(4);
        ms1.push(9);
        ms1.push(8);
        ms1.push(7);

        ms1.merge(ms2);
        ms1.display();
    }
} */