先序遍历：中、左、右
中序遍历：左、中、右
后序遍历：左、右、中
比如下面这科树
1
2 3
4 5 6 7
package com.sangfor.tree;
public class Node {
public int value;
public Node left;
public Node right;
public Node(int value) {
this.value = value;
}
}
package com.sangfor.tree;
public class ForEachTree {
public static void main(String[] args) {
Node node1 = new Node(1);
Node node2 = new Node(2);
Node node3 = new Node(3);
Node node4 = new Node(4);
Node node5 = new Node(5);
Node node6 = new Node(6);
Node node7 = new Node(7);
node1.left = node2;
node1.right = node3;
node2.left = node4;
node2.right = node5;
node3.left = node6;
node3.right = node7;
Syste
