TreeNode.java

public class TreeNode {
    int value;
    TreeNode leftNode;
    TreeNode rightNode;

    public void setValue(int value) {
        this.value = value;
    }
    public TreeNode(int value){
        this.value = value;
    }

    public void setLeftNode(TreeNode leftNode) {
        this.leftNode = leftNode;
    }

    public void setRightNode(TreeNode rightNode) {
        this.rightNode = rightNode;
    }
    public void frontShow(){
        System.out.println(value);
        if(leftNode!=null){
            leftNode.frontShow();
        }
        if(rightNode!=null){
            rightNode.frontShow();
        }
    }
    public void midShow(){
        if(leftNode!=null){
            leftNode.midShow();
        }
        System.out.println(value);
        if(rightNode!=null){
            rightNode.midShow();
        }
    }
    public void afterShow(){
        if(leftNode!=null){
            leftNode.afterShow();
        }
        if(rightNode!=null){
            rightNode.afterShow();
        }
        System.out.println(value);
    }
    public TreeNode frontSearch(int i){
        TreeNode target = null;
        if(this.value==i){
            return this;
        }else{
            if(leftNode!=null){
                target = leftNode.frontSearch(i);
            }
            if(target!=null){
                return target;
            }
            if(rightNode!=null){
                target = rightNode.frontSearch(i);
            }
        }
        return target;
    }
    public void delete(int i){
        TreeNode parent = this;
        if(parent.leftNode!=null&&parent.leftNode.value==i){
            parent.leftNode=null;
            return;
        }
        if(parent.rightNode!=null&&parent.rightNode.value==i){
            parent.rightNode=null;
            return;
        }
        parent=leftNode;
        if(parent!=null){
            parent.delete(i);
        }
        parent=rightNode;
        if(parent!=null){
            parent.delete(i);
        }
    }
}