SumOfDigits.java

package com.examplehub.maths;

public class SumOfDigits {

  /**
   * Sum of digits.
   *
   * @param number the number.
   * @return the sum of digits.
   */
  public static int sumOfDigits(long number) {
    number = Math.abs(number);
    int sum = 0;
    while (number != 0) {
      sum = (int) (sum + number % 10);
      number /= 10;
    }
    return sum;
  }

  /**
   * Sum of digits using byte array.
   *
   * @param number the number.
   * @return the sum of digits.
   */
  public static int sumOfDigitsSecond(int number) {
    byte[] bytes = (Math.abs(number) + "").getBytes();
    int sum = 0;
    for (byte temp : bytes) {
      sum += temp - '0';
    }
    return sum;
  }

  /**
   * Sum of digits using recursion.
   *
   * @param number the number.
   * @return the sum of digits.
   */
  public static int sumOfDigitsRecursion(int number) {
    number = Math.abs(number);
    return number < 10 ? number : number % 10 + sumOfDigits(number / 10);
  }
}