Path Sum

Given a binary tree and a sum, determine if the tree has a root-to-leaf path such that adding up all the values along the path equals the given sum.

For example:
Given the below binary tree and sum = 22,

              5
             / \
            4   8
           /   / \
          11  13  4
         /  \      \
        7    2      1

return true, as there exist a root-to-leaf path 5->4->11->2 which sum is 22.

public class Solution {
    public boolean hasPathSum(TreeNode root, int sum) {
       if(root==null)
          return false;
        if(root.left==null&&root.right==null&&root.val ==sum) return true;
        else{
            return hasPathSum(root.left,sum-root.val)||hasPathSum(root.right,sum-root.val);
        }
    }
}