Question

write a program in Java to check whether the provided number is an Armstrong one or not​

Answer 1

Armstrong Number - Java

Armstrong Numbers are those for which the sum of cubes of the digits is same as the original number.

For example, 371 is an Armstrong Number:

$\sf 3^3 = 27 \\ 7^3 = 343 \\ 1^3 = 1 \\\\\\ \to 3^3+7^3+1^3 = 27+343+1 = 371 \\\\ \implies \boxed{3^3+7^3+1^3 = 371}$

There are only six Armstrong numbers: 0, 1, 153, 370, 371 and 407.

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We need to write a Java program to check if a given number is an Armstrong Number or not.

Our general algorithm would be something like this:

• Take User input of number through Scanner
• Store its value in another variable for later comparison
• Initialise a sum variable to 0
• Run a loop to extract digits of the number
• In each iteration of the loop, add the cube of the digit to sum
• Finally, Compare the sum with the original value we stored earlier
• If both sum and original number are same, then the number is an Armstrong Number

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import java.util.Scanner;

public class ArmstrongNumber

{

   public static void main(String args[])

   {

       Scanner sc = new Scanner(System.in);

       

       System.out.println("A number is an Armstrong number, if the sum of cubes of the digits is equal to the original number.");

       System.out.print("Enter a number: ");

       long number = sc.nextLong(); //Taking User Input

   

       long originalValue = number; //Using another variable with same number to store original value

       long sum=0;  //Initialising sum to 0

       

       do

       {

           long digit = number % 10; //Extracting digit

           sum += digit * digit * digit;     //Adding the cube of the digit to sum

           number /= 10;       //Dividing by 10 for next digit in next loop iteration

       }

       while(number!=0);

       

       if (sum==originalValue)     //Comparing Sum of Cube of digits to original number

           System.out.println(originalValue+" is an Armstrong number");

       else

           System.out.println(originalValue+" is not an Armstrong number");

           

   }

}