leetcode Balanced Binary Tree

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 {

private int heightOfTree(TreeNode root) {
int height;
if (root == null) {
return -1;
}

int hleft=heightOfTree(root.left);
int rlegt=heightOfTree(root.right);
height=1+Math.max(hleft, rlegt);
return height;
}

public boolean isBalanced(TreeNode root) {
if (root == null) {
return true;
}
int height=heightOfTree(root.left)-heightOfTree(root.right);
if (height>1 || height<-1) {
return false;
}
if (!isBalanced(root.left)) {
return false;
}
if (!isBalanced(root.right)) {
return false;
}
return true;

}
}