balanced-binary-tree Java code

Given a binary tree, determine if it is height-balanced.
For this problem, a height-balanced binary tree is defined as a binary tree in which the depth of the two subtrees of every node never differ by more than 1.

/** * Definition for binary tree * public class TreeNode { *     int val; *     TreeNode left; *     TreeNode right; *     TreeNode(int x) { val = x; } * } */public class Solution {    public boolean isBalanced(TreeNode root) {        if(getHeight(root) == -1) return false;        return true;    }    private int getHeight(TreeNode root){        if(root == null) return 0;        int leftHeight = getHeight(root.left);        int rightHeight = getHeight(root.right);        if(leftHeight == -1 || rightHeight == -1) return -1;        int diff = Math.abs(leftHeight - rightHeight);        if(diff > 1) return -1;        return Math.max(leftHeight, rightHeight) + 1;    }}