Maximum Depth of Binary Tree

/**
* Definition for a binary tree node.
* public class TreeNode {
*     int val;
*     TreeNode left;
*     TreeNode right;
*     TreeNode(int x) { val = x; }
* }
*/
public class Solution {
int count = 0;
int max = 0;
public int maxDepth(TreeNode root) {
count++;
if(root != null) {
maxDepth(root.left);
count--;
max = Math.max(max,count);
maxDepth(root.right);
count--;
max = Math.max(max,count);
}
return max;
}
}