Java Program to Find the Sum of Digits of a Number

Introduction

Finding the sum of the digits of a number is a common programming task, especially useful in problems related to number theory and mathematics. This task involves breaking down a number into its individual digits and summing them up. This guide will walk you through writing a Java program that calculates the sum of the digits of a given number.

Problem Statement

Create a Java program that:

• Prompts the user to enter a number.
• Calculates the sum of the digits of the number.
• Displays the result.

Example:

• Input: 1234

• Output: "The sum of the digits of 1234 is 10"

• Input: 987

• Output: "The sum of the digits of 987 is 24"

Solution Steps

1. Read the Number: Use the Scanner class to take the number as input from the user.
2. Calculate the Sum of Digits: Use a loop to extract each digit and sum them up.
3. Display the Result: Print the sum of the digits.

Java Program

// Java Program to Find the Sum of Digits of a Number
// Author: https://www.rameshfadatare.com/

import java.util.Scanner;

public class SumOfDigits {
    public static void main(String[] args) {
        // Step 1: Read the number from the user
        try (Scanner scanner = new Scanner(System.in)) {
            System.out.print("Enter a number: ");
            int number = scanner.nextInt();
            
            // Step 2: Calculate the sum of digits
            int sum = calculateSumOfDigits(number);
            
            // Step 3: Display the result
            System.out.println("The sum of the digits of " + number + " is " + sum);
        }
    }
    
    // Method to calculate the sum of digits of a number
    public static int calculateSumOfDigits(int number) {
        int sum = 0;
        
        while (number != 0) {
            // Extract the last digit of the number
            int digit = number % 10;
            // Add the digit to the sum
            sum += digit;
            // Remove the last digit from the number
            number /= 10;
        }
        
        return sum;
    }
}

Explanation

Step 1: Read the Number

• The Scanner class is used to read an integer input from the user. The nextInt() method captures the input number.

Step 2: Calculate the Sum of Digits

• The calculateSumOfDigits() method calculates the sum of the digits:
  • The loop runs as long as the number is not zero.
  • In each iteration, the last digit of the number is extracted using number % 10.
  • The extracted digit is added to the sum.
  • The last digit is then removed from the number using integer division (number /= 10).

Step 3: Display the Result

• The program prints the sum of the digits using System.out.println().

Output Example

Example 1:

Enter a number: 1234
The sum of the digits of 1234 is 10

Example 2:

Enter a number: 987
The sum of the digits of 987 is 24

Conclusion

This Java program demonstrates how to find the sum of the digits of a given number. It covers essential concepts such as loops, arithmetic operations, and user input handling, making it a valuable exercise for beginners learning Java programming.