Java program to print sum of digits of a number

In Java, to print the sum of digits of a given number we can use loop concepts such as while loop or for loop. If the input number is 1234, then we need to add every digit of that number like 1+2+3+4 and print the output as 10.

In this article we will learn writing program in java to print the sum of digits of a given number. We will also see examples, detailed logic and program explanation for better understanding.

Required Knowledge

• Java programming basics
• Java Operators
• Loop Concepts

Problem Statement

We have to write a java program to print the sum of digits of a given number. The program should take integer as an input, and add each digit of that input integer one by one. And once all digit added, print the sum as output. This action should be done in our program.

Let’s see an example,

Example:

For input number 12, Output should be 3

Explanation:

Input integer number: 12

sum= 1+ 2 = 3 

Hence, for the input number 12, it's sum of digits is 3.

Logic to print the sum of digits of a given number

To find the sum of input integer, First we will take last digit and add it to the sum variable (initially sum should be kept as 0 to get proper result).

After adding the digit to sum, we should reduce the number by dividing it to 10 for further iterations and should add the last digit in this updated number to the sum. And we should repeat this process until input number become to 0.

Once input number become 0, it means we have visited each digits of the input number

Java program to print the sum of digits in a given number

Program 1: Using while loop

In the below program we are using while loop to print the sum of digits in of a given number.

import java.util.Scanner;
public class SumDigits {
	public static void main(String[] args) {
		Scanner s = new Scanner(System.in);
		System.out.println("Enter a number");
		int num = s.nextInt();
		int digit=0;
		int sum = 0;
		while (num != 0) {
			digit=num %10; // gives last digit and stores in digit
			sum+=digit;// adds digit to the sum
			num=num/10;// remove last digit from number
		}
		System.out.println("sum of the digits: "+sum);
		s.close();
	}
}

Output:

Enter a number
1345
sum of the digits: 13

Java program explanation to print the sum of digits in a given number

• The program starts by importing the Scanner class for input reading.
• Asks the user to enter a number.
• It reads and stores the number using nextInt() method of Scanner.
• Initializes digit and sum variables to 0.
• Enters a while loop that continues until num becomes 0.
• Inside the loop:
• Computes digit as the last digit of num using num % 10.
• Adds digit to sum.
• Updates num by removing its last digit using num / 10.
• After the loop completes (when num is 0), prints the sum of the digits.
• Closes the Scanner object to release resources.

Program 2: Using for loop

In the below program we are using for loop to print the sum of digits of a given number in Java.

import java.util.Scanner;
public class SumDigits {
	public static void main(String[] args) {
		Scanner s = new Scanner(System.in);
		System.out.println("Enter a number");
		int num = s.nextInt();
		int digit=0;
		int sum = 0;
		for (int i=num ;i != 0;i/=10) {
			digit=i %10; // gives last digit and stores in digit
			sum+=digit;// adds digit to the sum	
		} 
		System.out.println("sum of the digits: "+sum);
		s.close();
	}
}

Output:

Enter a number
23456
sum of the digits: 20

Java program explanation to print the sum of digits in a given number

• The program imports the Scanner class for input reading.
• Asks the user to enter a number and reads it using nextInt().
• Initializes variables digit to store each digit and sum to accumulate the sum of digits.
• Uses a for loop to iterate until num becomes 0.
• Inside the loop:
• Computes digit as the last digit of i using i % 10.
• Adds digit to sum.
• Updates i by removing its last digit using i /= 10.
• After the loop completes (when i is 0), prints the sum of the digits.
• Closes the Scanner object to release resources.

Conclusion

In this tutorial we have learnt writing the Java program to calculate the sum of the digits in a given number using while loop and for loop.

You can also check our awesome programs here

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Happy Coding !!