Iterate through each digit in a number

Question

I am trying to create a program that will tell if a number given to it is a \"Happy Number\" or not. Finding a happy number requires each digit in the number to be squared,

Answer 1

I wondered which method would be quickest to split up a positive number into its digits in Java, String vs modulo

  public static ArrayList splitViaString(long number) {

    ArrayList result = new ArrayList<>();
    String s = Long.toString(number);

    for (int i = 0; i < s.length(); i++) {
      result.add(s.charAt(i) - '0');
    }
    return result; // MSD at start of list
  }

vs

  public static ArrayList splitViaModulo(long number) {

    ArrayList result = new ArrayList<>();

    while (number > 0) {
      int digit = (int) (number % 10);
      result.add(digit);
      number /= 10;
    }
    return result; // LSD at start of list
  }

Testing each method by passing Long.MAX_VALUE 10,000,000 times, the string version took 2.090 seconds and the modulo version 2.334 seconds. (Oracle Java 8 on 64bit Ubuntu running in Eclipse Neon)

So not a lot in it really, but I was a bit surprised that String was faster