Happy Number

Write an algorithm to determine if a number is happy.

A happy number is a number defined by the following process: Starting with any positive integer, replace the number by the sum of the squares of its digits, and repeat the process until the number equals 1 (where it will stay), or it loops endlessly in a cycle which does not include 1. Those numbers for which this process ends in 1 are happy numbers.
1^2 + 9^2 = 82
8^2 + 2^2 = 68
6^2 + 8^2 = 100
1^2 + 0^2 + 0^2 = 1

public class Solution {    private int getNextHappy(int n) {        int sum = 0;        while (n != 0) {            sum += (n % 10) * (n % 10);            n /= 10;        }        return sum;    }    public boolean isHappy(int n) {        HashSet<Integer> hash = new HashSet<Integer>();        while (n != 1) {            if (hash.contains(n)) { //防止循环...                return false;            }            hash.add(n);            n = getNextHappy(n);        }        return true;    }}