JavaAlgorithms/Maths/Armstrong.java

package Maths;

/**
 * An Armstrong number is equal to the sum of the cubes of its digits. For example, 370 is an
 * Armstrong number because 3*3*3 + 7*7*7 + 0*0*0 = 370. An Armstrong number is often called
 * Narcissistic number.
 */
public class Armstrong {

  public static void main(String[] args) {
    assert (isArmStrong(0));
    assert (isArmStrong(1));
    assert (isArmStrong(153));
    assert (isArmStrong(1634));
    assert (isArmStrong(371));
    assert (!isArmStrong(200));
  }

  /**
   * Checks whether a given number is an armstrong number or not.
   *
   * @param number number to check
   * @return {@code true} if given number is armstrong number, {@code false} otherwise
   */
  private static boolean isArmStrong(int number) {
    int sum = 0;
    int temp = number;
    int numberOfDigits = 0;
    while (temp != 0) {
      numberOfDigits++;
      temp /= 10;
    }
    temp = number; /* copy number again */
    while (number > 0) {
      int remainder = number % 10;
      int power = 1;
      for (int i = 1; i <= numberOfDigits; power *= remainder, ++i)
        ;
      sum = sum + power;
      number /= 10;
    }
    return sum == temp;
  }
}