JavaAlgorithms/Maths/Armstrong.java

package strings;

/**
 * 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;
    }
}