LeetCode 404: Sum of Left Leaves

/**
* Definition for a binary tree node.
* public class TreeNode {
*     int val;
*     TreeNode left;
*     TreeNode right;
*     TreeNode(int x) { val = x; }
* }
*/
class Solution {
public int sumOfLeftLeaves(TreeNode root) {
return getSum(root, false);
}

private int getSum(TreeNode root, boolean isLeft) {
if (root == null) {
return 0;
}

if (root.left == null && root.right == null && isLeft) {
return root.val;
}

return getSum(root.left, true) + getSum(root.right, false);
}
}