Learn Java by Example: Java Program to Find the Sum of Natural Numbers using Recursion

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Java Program to Find the Sum of Natural Numbers using Recursion

In this program, you’ll learn to find the sum of natural number using recursion in Java. This is done with the help of a recursive function.

 


The positive numbers 1, 2, 3… are known as natural numbers. The program below takes a positive integer from the user and calculates the sum up to the given number.

 

Example: Sum of Natural Numbers Using Recursion


public class AddNumbers{

    public static void main(String[] args){
        int number = 20;
        int sum = addNumbers(number);
        System.out.println("Sum = " + sum);
    }

    public static int addNumbers(int num){
        if (num != 0)
            return num + addNumbers(num - 1);
        else
            return num;
    }
}

Output

Sum = 210

The number whose sum is to be found is stored in a variable number.

Initially, the addNumbers() is called from the main() function with 20 passed as an argument.

The number (20) is added to the result of addNumbers(19).

In the next function call from addNumbers() to addNumbers(), 19 is passed which is added to the result of addNumbers(18). This process continues until num is equal to 0.

When num is equal to 0, there is no recursive call and this returns the sum of integers to the main() function.

 

 

 

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