1.  public boolean isHappy(int n) {
    2.         HashSet<Integer> set = new HashSet<>();
    3.         while (n != 1){
    4.             int sum = 0;
    5.             while (n != 0) {
    6.                 sum +=Math.pow(n % 10, 2);
    7.                 n /= 10;
    8.             }
    9.             n = sum;
    10.             //防止无限循环
    11.             if (set.contains(n)) {
    12.                 break;
    13.             }
    14.             set.add(n);
    15.         }
    16.         return n == 1;
    17.     }