In this article, we will discuss and execute a simple Java program to check whether the given number is Armstrong number or not

Armstrong number:

• If the given number is equal to sum of their m^th power of each digits then the number is Armstrong number
  • where m is length of the given number
• For example, let’s assume given number is 153 and their sum of cubes is (1³ + 5³ + 3³) = (1 + 125 + 27) = 153, so given number 153 is Armstrong number
• Likewise, let’s take another number 1634 and their sum of 4^th power of each digits is (1⁴ + 6⁴ + 3⁴ + 4⁴) = (1 + 1296 + 81 + 256) = 1634, so given number 1634 is Armstrong number
• Let’s consider number 1234 and their sum of 4^th power of each digits is (1⁴ + 2⁴ + 3⁴ + 4⁴) = (1 + 16 + 81 + 216) = 314, so given number 1234 is not Armstrong number since original number and their sum of m^th power isn’t Equal

Armstrong number program steps:

1. First assign the original number in local variables for comparison at the end
2. Get the length of the given number for calculating their power of each digits in the given number
3. Now, iterate through while-loop until given number becomes zero
   1. Get the remainder after doing modulo of 10 –> which will give last digit of the given number
   2. Get the new number after dividing with 10 –> this step provide new number after removing last digit
   3. Inside While-loop, iterate using for-loop starting with 0 till (length-1) for calculating m^th power of the remainder
   4. After completion of for-loop, add the calculated value to the result variable
4. Finally compare original given number with the resulting number
   1. If both comes to be same/Equal then the given number is Armstrong number
   2. Otherwise it is not Armstrong number

ArmstrongNumber.java

package in.bench.resources.java.armstrong.number;

public class ArmstrongNumber {

	// main() method
	public static void main(String[] args) {

		System.out.println("1.Check for number 153 \n" 
				+ checkArmstrongNumber(153));

		System.out.println("\n2.Check for number 1634 \n" 
				+ checkArmstrongNumber(1634));

		System.out.println("\n3.Check for number 1234 \n" 
				+ checkArmstrongNumber(1234));
	}


	/**
	 * This method checks whether the given number is Armstrong number or not
	 * 
	 * @param number
	 * @return
	 */
	public static String checkArmstrongNumber(int number) {

		// local variables
		int remainder = 0;
		int result = 0;
		int length = 0;

		// assign original number for comparison at the end
		int dividend = number;


		// get length of given number
		length = String.valueOf(number).length();


		// get remainder and quotient by iterating inside while-loop
		while(number > 0) {

			// get 1st remainder
			remainder = number % 10; // 3 5 1

			// get 1st quotient
			number = number / 10; // 15 1 0

			int tempMul = 1;

			for(int index=0; index<length; index++) {

				// 
				tempMul = tempMul * remainder; // 3 9 27 // 5 25 125 // 1 1 1
			}

			// result
			result = result + tempMul; // 27 + 125 + 1
		}


		if(dividend == result) {
			return dividend + " is a Armstrong number";
		}
		else {
			return dividend + " is not a Armstrong number";
		}
	}
}

Output:

1.Check for number 153 
153 is a Armstrong number

2.Check for number 1634 
1634 is a Armstrong number

3.Check for number 1234 
1234 is not a Armstrong number

Note : There are various other ways to check whether the given number is Armstrong number or not

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Happy Coding !!
Happy Learning !!