用非递归方式实现二叉树先序便利

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;

import java.util.Stack;

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 =