Check Whether the Given Number Is Armstrong Number or Not Example...

Introduction

Check whether the given number is Armstrong number or not is a classic Java console program that demonstrates the concept with complete source code and sample output. Calculation programs apply formulas to solve geometry, statistics and numeric problems.

This tutorial walks through the program line by line, explains how the logic works, and highlights best practices you can apply in your own code.

Definition

An Armstrong number of three digits is an integer such that the sum of the cubes of its digits is equal to the number itself. For example, 371 is an Armstrong number since 3**3 + 7**3 + 1**3 = 371.

Check whether the given number is Armstrong number or not Example Program

import java.util.Scanner;

public class ArmstrongNumberCheck {
	public static boolean isArmstrong(int input) {
		String str = input + "";
		int size = str.length();
		int in = input;
		int sum = 0;
		while (in != 0) {
			int lastDigit = in % 10;
			sum = sum + (int) Math.pow(lastDigit,size);
			in = in / 10;
		}
		if (sum == input) {
			return true;
		} 
		else {
			return false;
		}
	}
	public static void main(String[] args) {
		Scanner in = new Scanner(System.in);
		System.out.print("Enter a number: ");
		int inputNumber = in.nextInt();
		boolean result = isArmstrong(inputNumber);
		if (result) {
			System.out.println(inputNumber + " is an Armstrong number");
		} 
		else {
			System.out.println(inputNumber + " is not an Armstrong number");
		}
	}
}

Sample Output

Enter a number: 5678
5678 is not an Armstrong number

When to use

Use these formulas in homework tools, engineering calculators or anywhere repeated numeric computation is needed.

How it works

1. Execution begins in the main method — the JVM calls this method when you run the class.

2. import java.util.Scanner; imports a class used later in the program.

3. String str = input + ""; updates a variable used in the calculation or output.

4. int size = str.length(); updates a variable used in the calculation or output.

5. int in = input; updates a variable used in the calculation or output.

6. int sum = 0; updates a variable used in the calculation or output.

7. while (in != 0) { updates a variable used in the calculation or output.

8. The if statement runs the nested code only when the condition is true.

Best Practices

• Use meaningful variable and class names that describe their purpose.
• Compile and run the program locally — modify values to see how output changes.
• Read compiler errors carefully; they usually point to the exact line to fix.

Common Mistakes

• Copying code without understanding each line — practice by changing one statement at a time.
• Mismatching the public class name and the .java filename.
• Forgetting semicolons at the end of statements.