package Maths;

public class SumOfDigits {
 public static void main(String[] args) {
 assert sumOfDigits(-123) == 6 && sumOfDigitsRecursion(-123) == 6 && sumOfDigitsFast(-123) == 6;

 assert sumOfDigits(0) == 0 && sumOfDigitsRecursion(0) == 0 && sumOfDigitsFast(0) == 0;

 assert sumOfDigits(12345) == 15
 && sumOfDigitsRecursion(12345) == 15
 && sumOfDigitsFast(12345) == 15;
 }

 /**
 * Calculate the sum of digits of a number
 *
 * @param number the number contains digits
 * @return sum of digits of given {@code number}
 */
 public static int sumOfDigits(int number) {
 number = number < 0 ? -number : number; /* calculate abs value */
 int sum = 0;
 while (number != 0) {
 sum += number % 10;
 number /= 10;
 }
 return sum;
 }

 /**
 * Calculate the sum of digits of a number using recursion
 *
 * @param number the number contains digits
 * @return sum of digits of given {@code number}
 */
 public static int sumOfDigitsRecursion(int number) {
 number = number < 0 ? -number : number; /* calculate abs value */
 return number < 10 ? number : number % 10 + sumOfDigitsRecursion(number / 10);
 }

 /**
 * Calculate the sum of digits of a number using char array
 *
 * @param number the number contains digits
 * @return sum of digits of given {@code number}
 */
 public static int sumOfDigitsFast(int number) {
 number = number < 0 ? -number : number; /* calculate abs value */
 char[] digits = (number + "").toCharArray();
 int sum = 0;
 for (int i = 0; i < digits.length; ++i) {
 sum += digits[i] - '0';
 }
 return sum;
 }
}