Java Program to Find Sum of Digits of a Number by Using Recursion

In the previous article, we have discussed about Java Program to Find Sum of All Numbers in an Array by Using Recursion

In this program we are going to see how to find sum of digits of a number using by Recursion in Java programming language.

Java Program to Find Sum of Digits of a Number by Using Recursion

Lets assume there is a number say N = 1234

Then the sum of the digits of N = 1+2+3+4 = 10

Now let’s see different ways to find sum of digits of a number by using Recursion.

By Using Static Input and Recursion
By Using User Input and Recursion

Method-1: Java Program to Find Sum of Digits of a Number By Using Static Input and Recursion

Approach:

Declare and initialize an integer variable say ‘n’
Call a user defined method calculateSum() and pass ‘n’ as parameter.
Inside the user defined method we will check the number. If the number is <=0 then the method returns 0 else it calls the same method as calculateSum(n/10) + n%10 and return the value to the main method.
Now the value of the user defined method calculateSum() is stored in an integer variable say ‘sum’.
Print the value of sum

Program:

import java.util.*;
import java.io.*;
public class Main 
{
    public static void main(String[] args)
    {
        // declare and initialize an integer variable ‘n’ 
        int n = 7869;
        //call the user defined method calculateSum()
        //and store the result value inside an integer variable say ‘sum’
        int sum = calculateSum(n);
        System.out.println("The sum of digits of the number is: "+sum);
    }
    
    //calculateSum() method 
    static int calculateSum(int n)
    {
        //checking if if number is less than 0 then returning 0 as result
        if (n <= 0)
            return 0;
        //else adding the digits of number by using recursion technique
        else
            return n%10 + calculateSum(n/10);
    }
}

Output:

The sum of digits of the number is: 30

Method-2: Java Program to Find Sum of Digits of a Number By Using Dynamic Input and Recursion

Approach:

Declare and initialize an integer variable say ‘n’
Call a user defined method calculateSum() and pass ‘n’ as parameter.
Inside the user defined method we will check the number. If the number is <=0 then the method returns 0 else it calls the same method as calculateSum(n/10) + n%10 and return the value to the main method.
Now the value of the user defined method calculateSum() is stored in an integer variable say ‘sum’.
Print the value of sum

Program:

import java.util.*;
import java.io.*;
public class Main 
{
    public static void main(String[] args)
    {
        // create a scanner class object
        Scanner s = new Scanner(System.in);
        //Taking input of a number
        System.out.println("Enter the number:");
        int n = s.nextInt();
        //call the user defined method calculateSum()
        //and store the result value inside an integer variable say ‘sum’
        int sum = calculateSum(n);
        System.out.println("The sum of digits of the number is: "+sum);
    }
    
    //calculateSum() method 
    static int calculateSum(int n)
    {
        //checking if if number is less than 0 then returning 0 as result
        if (n <= 0)
            return 0;
        //else adding the digits of number by using recursion technique
        else
            return n%10 + calculateSum(n/10);
    }
}

Output:

Enter the number:
2543
The sum of digits of the number is: 14

Enhancing programming skills is very important no matter what language you have chosen. So, practice frequently with these simple java programs examples and excel in coding the complex logic.

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