A number is armstrong if the sum of the cubes of digit of number is equal to the number.
ex- 407 = 4*4*4 + 0*0*0 + 7*7*7 

import java.util.Scanner;

public class ArmstrongNum{
    public static void main(String[] args){
        Scanner in = new Scanner(System.in);
        System.out.println(“Enter a number which you want to check whether that is armstrong or not: “);
        int n = in.nextInt();
        int a = n, r=0, s=0;
        
        while(a!=0){
            r = a%10;
            a = a/10;
            s = s + r*r*r;
        }
        if(s==n){
            System.out.println(“Number “+n+” is an armstrong number.”);
        }else{
            System.out.println(“Number “+n+” is not an armstrong number.”);
        }    
    }
}

output

Enter a number which you want to check whether that is armstrong or not: 
407
Number 407 is an armstrong number.

 

Source: http://selenium-makeiteasy.blogspot.com