Java Program to Check Armstrong Number or Not

• Write a java program to check whether a number is armstrong number or not.

In this java program, we have to check whether a given number is an armstrong number or not and print the result on screen.
Armstrong number is a number that is equal to the sum of cubes of its digits.
Examples of Armstrong Numbers : 0, 1, 2, 3, 153, 370, 407 etc.

For Example,
153 is an Armstrong number
153 = 1*1*1 + 5*5*5 + 3*3*3

100 is not an Armstrong number
100 is not equal to 1*1*1 + 0*0*0 + 0*0*0
Algorithm to check for Armstrong number
Let N be the given.
• Find the cubic sum of digits of N, and store it in sum variable.
• Compare N and sum.
• If both are equal then N is Armstrong number otherwise not an Armstrong number.

Java program to check Armstrong number or not using loop

This program first takes a number as input from user and stores it in variable 'N'. It makes a copy of number in variable 'temp'. Then using a while loop, it calculates the sum of cubes of every digit of temp(loop will terminate when temp becomes zero) and stores it in a 'sum' variable. If sum is equal to N then it is an Armstrong number otherwise N is not an Armstrong number.

```package com.tcc.java.programs;

import java.util.Scanner;

/**
* Java Program to check Armstrong Number
*/
public class ArmstrongNumber {
public static void main(String[] args) {
int N, temp, sum = 0, rightDigit;
Scanner scanner;
scanner = new Scanner(System.in);

System.out.println("Enter an Integer");
N = scanner.nextInt();

temp = N;
/*
* Find the sum of cubes of every digit of N
*/
while (temp != 0) {
rightDigit = temp % 10;
sum = sum + (rightDigit * rightDigit * rightDigit);
temp = temp / 10;
}
/*
* Check if sum is equal to N, then N is a armstrong number otherwise
* not an armstrong number
*/
if (sum == N) {
// N is armstrong number
System.out.format("%d is Armstrong Number", N);
} else {
// N is not an armstrong number
System.out.format("%d is Not an Armstrong Number", N);
}
}
}
```
Output
```Enter an Integer
407
407 is Armstrong Number
```
```Enter an Integer
120
120 is Not an Armstrong Number
```

Java program to check Armstrong number using function

This java program is similar to above program except here we are using a user defined function "isArmstrongNumber" which takes an integer input and prints whether input number is armstrong number or not.

```package com.tcc.java.programs;

import java.util.Scanner;

/**
* Java Program to check Armstrong Number
*/
public class ArmstrongNumberCheckFunction {
public static void main(String[] args) {
int N;
Scanner scanner;
scanner = new Scanner(System.in);

System.out.println("Enter an Integer");
N = scanner.nextInt();
/*
* Calling isArmstrongNumber method to check if N is armstrong or not.
*/
isArmstrongNumber(N);
}

public static void isArmstrongNumber(int N) {
int sum = 0, rightDigit, temp;
temp = N;
while (temp != 0) {
rightDigit = temp % 10;
sum = sum + (rightDigit * rightDigit * rightDigit);
temp = temp / 10;
}
/*
* Check if sum is equal to N, then N is a armstrong number otherwise
* not an armstrong number
*/
if (sum == N) {
// N is armstrong number
System.out.format("%d is Armstrong Number", N);
} else {
// N is not an armstrong number
System.out.format("%d is Not an Armstrong Number", N);
}
}
}
```
Output
```Enter an Integer
407
407 is Armstrong Number
```

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