202. Happy Number java

https://leetcode.com/problems/happy-number/?envType=study-plan&id=programming-skills-i 

class Solution {
  public boolean isHappy(int n) {

    int sum = 0;
    ArrayList<Integer> arraylist = new ArrayList();

    while (true) {

      System.out.println("start n:" + n);

      while (n != 0) {
        int tmp = n % 10;
        n = n / 10 ;
        sum += Math.pow(tmp, 2);
      }

      System.out.println("calculated sum:" + sum);

      if (sum == 1) {
        return true;
      }
      else {
        if (arraylist.contains(sum)){
          System.out.println("반복되는 숫자입니다.");
          break;
        }
        else{
          arraylist.add(sum);
          n = sum;
          sum = 0;
          System.out.println("다시 반복합니다.");
        }
      }
    }
    return false;
  }