Java Program to Identify Armstrong Numbers Using For Loop

What Is an Armstrong Number?

An Armstrong number (also known as a narcissistic number) is a number that equals the sum of its own digits each raised to the power of the total number of digits.

Mathematically, for a number with digits x, y, … z and n digits, the following holds:

xy…z = xn + yn + … + zn

Examples of Armstrong numbers include:

0, 1, 4, 5, 9, 153, 371, 407, 8208, …

Java Program to Check If a Number Is an Armstrong Number

Below is a compact Java implementation that verifies whether a given integer is an Armstrong number. The algorithm iterates over each digit, accumulates the cube of the digit (since we’re focusing on three‑digit numbers), and compares the sum to the original number.

// Check whether a number is an Armstrong number using a while loop
package com.guru99;

public class ArmstrongNumber {

    public static void main(String[] args) {
        int inputArmstrongNumber = 153; // Number to test
        int tempNumber, digit, digitCubeSum = 0;

        tempNumber = inputArmstrongNumber;
        while (tempNumber != 0) {
            System.out.println("Current Number is " + tempNumber);
            digit = tempNumber % 10;
            System.out.println("Current Digit is " + digit);
            digitCubeSum += digit * digit * digit;
            System.out.println("Current digitCubeSum is " + digitCubeSum);
            tempNumber /= 10;
        }

        if (digitCubeSum == inputArmstrongNumber)
            System.out.println(inputArmstrongNumber + " is an Armstrong Number");
        else
            System.out.println(inputArmstrongNumber + " is not an Armstrong Number");
    }
}

Output

Current Number is 153
Current Digit is 3
Current digitCubeSum is 27
Current Number is 15
Current Digit is 5
Current digitCubeSum is 152
Current Number is 1
Current Digit is 1
Current digitCubeSum is 153
153 is an Armstrong Number

Java Program to List All Armstrong Numbers From 0 to 999

The following program demonstrates how to enumerate every Armstrong number in the 0‑999 range. It leverages a for loop for the range and a while loop to process each candidate.

// Enumerate Armstrong numbers between 0 and 999
package com.guru99;

public class ArmstrongNumber {

    public static void main(String[] args) {
        for (int inputArmstrongNumber = 0; inputArmstrongNumber < 1000; inputArmstrongNumber++) {
            int tempNumber = inputArmstrongNumber;
            int digitCubeSum = 0;

            while (tempNumber != 0) {
                int digit = tempNumber % 10;
                digitCubeSum += digit * digit * digit;
                tempNumber /= 10;
            }

            if (digitCubeSum == inputArmstrongNumber)
                System.out.println(inputArmstrongNumber + " is an Armstrong Number");
        }
    }
}

Output

0 is an Armstrong Number
1 is an Armstrong Number
153 is an Armstrong Number
370 is an Armstrong Number
371 is an Armstrong Number
407 is an Armstrong Number