java 实现简单树结构

public class MyBtree {    private Node root;    class Node{        private int data;        private Node left;        private Node right;        public void add(Node node) {            if (this.data > node.data){                if(this.left == null){                    this.left = node;                }else{                    this.left.add(node);                }            }            if(this.data < node.data){                if(this.right == null){                    this.right = node;                }else{                    this.right.add(node);                }            }        }        public void zhongxu() {            if(this.left != null){                this.left.zhongxu();            }            if(this.right != null){                this.right.zhongxu();            }            System.out.println(this.data);        }    }    public  void add(int data){        Node node = new Node();        node.data = data;        if (root==null){            root = node;        }else {            root.add(node);        }    }    public void zhongxu() {        root.zhongxu();    }}