Java Program for Sum the digits of a given number

Given a number, find the sum of its digits.
Example : 

Input : n = 687
Output : 21

Input : n = 12
Output : 3

1. Iterative:

Java

// Java program to compute
// sum of digits in number.
import java.io.*;

class GFG {

    /* Function to get sum of digits */
    static int getSum(int n)
    {
        int sum = 0;

        while (n != 0)
        {
            sum = sum + n % 10;
            n = n/10;
        }

    return sum;
    }

    // Driver program
    public static void main(String[] args)
    {
        int n = 687;

        System.out.println(getSum(n));
    }
}

// This code is contributed by Gitanjali

C++

// Include header file
#include <iostream>
#include <string>
#include <vector>

class GFG
{
    // Function to get sum of digits
    public:
    static int getSum(int n)
    {
        int sum = 0;
        while (n != 0)
        {
            sum = sum + n % 10;
            n = n / 10;
        }
        return sum;
    }
    // Driver program
    static void main(std::vector<std::string> &args)
    {
        int n = 687;
        std::cout << GFG::getSum(n) << std::endl;
    }
};
int main(int argc, char **argv){
    std::vector<std::string> parameter(argv + 1, argv + argc);
    GFG::main(parameter);
    return 0;
};

C#

// Include namespace system
using System;


public class GFG
{
    // Function to get sum of digits
    public static int getSum(int n)
    {
        var sum = 0;
        while (n != 0)
        {
            sum = sum + n % 10;
            n = (int)(n / 10);
        }
        return sum;
    }
    // Driver program
    public static void Main(String[] args)
    {
        var n = 687;
        Console.WriteLine(GFG.getSum(n));
    }
}

Output

21

Time Complexity: O(|n|)
Auxiliary Space: O(1)

How to compute in single line?

Java

// Java program to compute
// sum of digits in number.
import java.io.*;

class GFG {

    /* Function to get sum of digits */
    static int getSum(int n)
    {
        int sum;

        /* Single line that calculates sum */
        for (sum = 0; n > 0; sum += n % 10,
                                  n /= 10);

        return sum;
    }

    // Driver code
    public static void main(String[] args)
    {
        int n = 687;

        System.out.println(getSum(n));
    }
}

// This code is contributed by Gitanjali

Output

21

Time Complexity: O(|n|)
Auxiliary Space: O(1)

2. Recursive

Java

// Java program to compute
// sum of digits in number.
import java.io.*;

class GFG {

    /* Function to get sum of digits */
    static int sumDigits(int no)
    {
        return no == 0 ? 0 : no%10 +
                  sumDigits(no/10) ;
    }

    // Driver code
    public static void main(String[] args)
    {
    int n = 687;

    System.out.println(sumDigits(n));
    }
}

// This code is contributed by Gitanjali

Output

21

Time Complexity: O(log₁₀n)
Auxiliary Space: O(log₁₀n)

Please refer complete article on Program for Sum the digits of a given number for more details!