Prove safety Offer: Mirror binary tree (java version)

Title Description

Operation of a given binary tree, the binary tree is converted into a source image.
The binary image is defined:

源二叉树 
    	    8
    	   /  \     
    	  6   10
    	 / \  / \
    	5  7 9  11
镜像二叉树
    	    8
    	   /  \
    	  10   6
    	 / \  / \
    	11 9 7   5

Recursive version

/**
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 ;
        if(root.left==null && root.right==null)
            return;
        TreeNode temp = root.left;
        root.left = root.right;
        root.right = temp;
        if(root.left!=null)
            Mirror(root.left);
        if(root.right!=null)
            Mirror(root.right);
    }
}

Non-recursive version

public class Solution {
    public void Mirror(TreeNode root) {
        if(root==null)
            return ;
        Stack<TreeNode> stack = new Stack<>();
        stack.push(root);
        while(!stack.isEmpty()){
            TreeNode node = stack.pop();
            if(node.left!=null || node.right!=null){
                TreeNode temp = node.left;
                node.left = node.right;
                node.right = temp;
            }
            if(node.left!=null)
                stack.push(node.left);
            if(node.right!=null)
                stack.push(node.right);
        }
    }
}