Armstrong number

An Armstrong number (also known as a narcissistic number or pluperfect digital invariant) is a number that is equal to the sum of its own digits each raised to the power of the number of digits. For example, 153 is an Armstrong number because 13+53+33=1531^3 + 5^3 + 3^3 = 15313+53+33=153. This concept can be extended to numbers with any number of digits.

This example demonstrates how to check if a given number is an Armstrong number in Java. The program includes a method to calculate the sum of the digits raised to the power of the number of digits and then compares this sum to the original number.

Code Example

import java.util.Scanner;

public class ArmstrongNumberCheck {

    // Method to check if a number is an Armstrong number
    public static boolean isArmstrong(int number) {
        int originalNumber = number;
        int sum = 0;
        int numberOfDigits = String.valueOf(number).length();

        while (number != 0) {
            int digit = number % 10;
            sum += Math.pow(digit, numberOfDigits);
            number /= 10;
        }

        return sum == originalNumber;
    }

    public static void main(String[] args) {
        Scanner scanner = new Scanner(System.in);

        System.out.print("Enter a number: ");
        int number = scanner.nextInt();

        if (isArmstrong(number)) {
            System.out.println(number + " is an Armstrong number.");
        } else {
            System.out.println(number + " is not an Armstrong number.");
        }

        scanner.close();
    }
}

Code Explanation

Class Definition

public class ArmstrongNumberCheck {

This line defines a new class named ArmstrongNumberCheck. This class contains methods to check if a number is an Armstrong number and the main method to execute the program.

Method to Check if a Number is an Armstrong Number

Variables Initialization

int originalNumber = number;
int sum = 0;
int numberOfDigits = String.valueOf(number).length();

• originalNumber stores the original number to compare later.
• sum is initialized to 0 and will store the sum of the digits each raised to the power of the number of digits.
• numberOfDigits calculates the number of digits in the number by converting the number to a string and getting its length.

Loop to Calculate the Sum

while (number != 0) {
    int digit = number % 10;
    sum += Math.pow(digit, numberOfDigits);
    number /= 10;
}

• A while loop extracts digits from the end of number.
• digit stores the last digit of the number.
• sum is updated by adding the current digit raised to the power of numberOfDigits.
• number is updated by removing the last digit (integer division by 10).

Returning the Result

return sum == originalNumber;

The method returns true if the calculated sum equals the original number, indicating it is an Armstrong number; otherwise, it returns false.

Main Method

Reading User Input

Scanner scanner = new Scanner(System.in);

System.out.print("Enter a number: ");
int number = scanner.nextInt();

These lines create a Scanner object to read input from the user and prompt the user to enter a number.

Checking and Displaying the Result

if (isArmstrong(number)) {
    System.out.println(number + " is an Armstrong number.");
} else {
    System.out.println(number + " is not an Armstrong number.");
}

These lines check if the entered number is an Armstrong number using the isArmstrong method and display the result.