Armstrong number program in java

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Last Updated : 02/09/2018

Posted By :- jaiprakash

An Armstrong number is a number that is equal to the sum of the digits in a number raised to the power of a number of digits in the number. For example: If we take 371, it is an Armstrong number as the number of digits here is 3, so

371 = 3³ + 7³ + 1³ = 27 + 343 + 1 = 371

Similarly, 153 is Armstrong because 1³ + 5³ + 3³ equals to 153. Another Example is 9474, here the number of digits is 4, so

9474 = 9⁴ + 4⁴ + 7⁴ + 4⁴ = 6561 + 256 + 2401 + 256 = 9474.

And yes, 0 and 1 are also Armstrong number.

Java program for armstrong number

Now, as we know the concept of armstrong number, Let's create the Java program for Armstrong number using while loop

package com.armstrong;

import java.util.Scanner;

public class ArmstrongNumberCheck {
	public static void main(String args[])
	   {
	      int number, sum = 0;
	 
	      Scanner in = new Scanner(System.in);
	      System.out.println("Enter a number to check if it is an armstrong number");      
	      number = in.nextInt();	 	      
	 
	     /* Converting Integer to String. It'll help to find number of
        digits in the Integer by using length() */
	      String temp = number + "";
	      //get number length
	      int numLength = temp.length();
	      //copy the main Number in a variable
	      int numCopy = number;	     
	      
	      //loop all the numbers until remainder is 0
	      while(numCopy != 0 ){
		       int remainder = numCopy % 10;
		       // using Math.pow to get digit raised to the power
		       // total number of digits
		       sum = sum + (int)Math.pow(remainder, numLength);
		       numCopy = numCopy/10;
	      }
	      
	      System.out.println("sum is " + sum );
	 
	      if (number == sum )
	      {
	         System.out.println( number + " is an armstrong number.");
	      }
	      else
	      {
	         System.out.println(number+ " is not an armstrong number.");  
	      }
	      in.close();
	      
	   }
}

Output:

Enter a number to check if it is an armstrong number
9474
sum is 9474
9474 is an armstrong number.

Enter a number to check if it is an armstrong number
121
sum is 10
121 is not an armstrong number.

Enter a number to check if it is an armstrong number
371
sum is 371
371 is an armstrong number.

Program to generate Armstrong number up too N values in Java

package com.armstrong;

import java.util.Scanner;

public class ArmstrongNumberCheck {
	public static void main(String args[])
	   {
	      int number, sum = 0,n;
	 
	      Scanner in = new Scanner(System.in);
	      System.out.println("Enter a number up to which you want to check armstrong number");      
	      n = in.nextInt();	 	      
	      for(int i=0; i<n; i++) 
	      {
	    	  
	      number=i;
	      /* Converting Integer to String. It'll help to find number of
	        digits in the Integer by using length() */
	      String temp = number + "";
	      //get number length
	      int numLength = temp.length();
	      //copy the main Number in a variable
	      int numCopy = number;	     
	      
	      //loop all the numbers until remainder is 0
	      while(numCopy != 0 ){
		       int remainder = numCopy % 10;
		       // using Math.pow to get digit raised to the power
		       // total number of digits
		       sum = sum + (int)Math.pow(remainder, numLength);
		       numCopy = numCopy/10;
	      }
	      
	      
	 
	      if (number == sum )
	      {
	         System.out.println( number + " is an armstrong number.");
	      }
              //set to sum=0 again for next value
	       sum=0;
	      }
	      in.close();
	      
	   }
}

Output:

Enter a number up to which you want to check armstrong number
500
0 is an armstrong number.
1 is an armstrong number.
2 is an armstrong number.
3 is an armstrong number.
4 is an armstrong number.
5 is an armstrong number.
6 is an armstrong number.
7 is an armstrong number.
8 is an armstrong number.
9 is an armstrong number.
153 is an armstrong number.
370 is an armstrong number.
371 is an armstrong number.
407 is an armstrong number.