Maximum Depth of Binary Tree | LeetCode

/**
 * Definition for binary tree
 * public class TreeNode {
 *     int val;
 *     TreeNode left;
 *     TreeNode right;
 *     TreeNode(int x) { val = x; }
 * }
 */
public class Solution {
    public int maxDepth(TreeNode root)
    {
        if (root == null)
        {    
            return 0;
        }
        
        int left = maxDepth(root.left);
        int right = maxDepth(root.right);
        
        return max(left, right) + 1;
    }
    
    int max(int x, int y)
    {
        return x > y ? x : y;
    }
}