二叉树的镜像java实现

操作给定的二叉树，将其变换为源二叉树的镜像。

/**public class TreeNode {    int val = 0;    TreeNode left = null;    TreeNode right = null;    public TreeNode(int val) {        this.val = val;    }}*/import java.util.*;public class Solution {    public void Mirror(TreeNode root) {         if(root == null) return;        Stack<TreeNode> stack = new Stack<TreeNode>();        stack.push(root);        while(!stack.empty()) {            TreeNode node = stack.pop();            if(node.left != null || node.right != null) {                TreeNode nodeLeft = node.left;                TreeNode nodeRight = node.right;                node.left = nodeRight;                node.right = nodeLeft;            }            if(node.left != null) stack.push(node.left);            if(node.right != null) stack.push(node.right);        }    }}