Java Program to Check Armstrong Number

May 19, 2023

What is an Armstrong ?

An Armstrong number, also known as a narcissistic number, is a number that is the sum of its own digits when each digit is raised to the power of the number of digits in the number. For example, 371 is an Armstrong number because 3^3 + 7^3 + 1^3 = 371.

Understanding Armstrong numbers can be a fun way to explore the world of numbers and their intriguing properties.

Characteristics of Armstrong Numbers

Armstrong numbers have some interesting characteristics:

They are positive integers.
The number of digits in an Armstrong number is finite.
The sum of each digit raised to the power of the total number of digits results in the original number itself.
Armstrong numbers are relatively rare compared to other numbers.

Algorithm for Armstrong Number in Java

Define a function isArmstrongNumber() that takes an integer num as input and returns a boolean value.
Declare a variable originalNum and set it equal to num.
Convert num to a string and find the length of the string. This will give us the number of digits in num.
Declare a variable sum and set it to 0. This will be used to store the sum of the digits raised to the power of the number of digits.
Begin a loop that will iterate as long as num is greater than 0.
Inside the loop, find the last digit of num by using the modulus operator (%) to get the remainder when num is divided by 10.
Raise the digit to the power of the number of digits, and add the result to sum.
Divide num by 10 to remove the last digit.
End the loop.
After the loop, check if originalNum is equal to sum. If it is, return true. Otherwise, return false.

Note: that the "IS NULL" operator can only be used with columns that allow NULL values. If a column has a "NOT NULL" constraint, it means it cannot have NULL values, and using "IS NULL" with such columns will not yield any results.

Here is a pseudo-code algorithm for checking whether a given number is an Armstrong number:

FUNCTION isArmstrongNumber(num: INTEGER) -> BOOLEAN:
    originalNum = num
    numOfDigits = LENGTH(num AS STRING)
    sum = 0
    WHILE num > 0:
        digit = num MOD 10
        sum = sum + digit^numOfDigits
        num = num DIV 10
    END WHILE
    RETURN originalNum == sum
END FUNCTION

Here are a few examples of Armstrong numbers:

153 (1^3 + 5^3 + 3^3 = 153)
371 (3^3 + 7^3 + 1^3 = 371)
9474 (9^4 + 4^4 + 7^4 + 4^4 = 9474)

Example :

Run

public class Main {
    public static void main(String[] args) {
        int num = 153;
        if (isArmstrongNumber(num)) {
            System.out.println(num + " is an Armstrong number.");
        } else {
            System.out.println(num + " is not an Armstrong number.");
        }
    }

    public static boolean isArmstrongNumber(int num) {
        int originalNum = num;
        int numOfDigits = String.valueOf(num).length();
        int sum = 0;
        while (num > 0) {
            int digit = num % 10;
            sum = sum + (int) Math.pow(digit, numOfDigits);
            num = num / 10;
        }
        return originalNum == sum;
    }
}

Output :

153 is an Armstrong number.

Explanation : This program defines a function isArmstrongNumber() that takes an integer num as input and returns a boolean value indicating whether num is an Armstrong number. The main() method calls the isArmstrongNumber() function with the value 153, and prints a message to the console indicating whether the number is an Armstrong number or not. You can replace 153 with any other integer to test whether it is an Armstrong number.

Here is an example of the input and output format when using the program to check whether a number is an Armstrong number:

Example :

Run

import java.util.Scanner;

public class Main {
    public static void main(String[] args) {
        Scanner scanner = new Scanner(System.in);
        while (true) {
            System.out.print("Enter a number (or q to quit): ");
            String input = scanner.nextLine();
            if (input.equals("q")) {
                break;
            }
            int num = Integer.parseInt(input);
            if (isArmstrongNumber(num)) {
                System.out.println(num + " is an Armstrong number.");
            } else {
                System.out.println(num + " is not an Armstrong number.");
            }
        }
    }

    public static boolean isArmstrongNumber(int num) {
        int originalNum = num;
        int numOfDigits = String.valueOf(num).length();
        int sum = 0;
        while (num > 0) {
            int digit = num % 10;
            sum = sum + (int) Math.pow(digit, numOfDigits);
            num = num / 10;
        }
        return originalNum == sum;
    }
}

Input :

Enter a number (or q to quit): 153

Output :

153 is an Armstrong number.

Note : This modified program will prompt the user to enter a number, and will keep prompting until the user enters “q” to quit. For each number entered, the program will print a message indicating whether the number is an Armstrong number or not.

Prime Course Trailer

Related Banners

Get PrepInsta Prime & get Access to all 200+ courses offered by PrepInsta in One Subscription

Get over 200+ course One Subscription

Courses like AI/ML, Cloud Computing, Ethical Hacking, C, C++, Java, Python, DSA (All Languages), Competitive Coding (All Languages), TCS, Infosys, Wipro, Amazon, DBMS, SQL and others

Java Program to Check Armstrong Number

What is an Armstrong ?

Characteristics of Armstrong Numbers

Algorithm for Armstrong Number in Java

Here is a pseudo-code algorithm for checking whether a given number is an Armstrong number:

Here are a few examples of Armstrong numbers:

Example :

Output :

Here is an example of the input and output format when using the program to check whether a number is an Armstrong number:

Example :

Input :

Output :

Prime Course Trailer

Related Banners

Get over 200+ course One Subscription

Checkout list of all the video courses in PrepInsta Prime Subscription

Checkout list of all the video courses in PrepInsta Prime Subscription