Java Program to Add All the Numbers from 1 to n by Using Recursion

In the previous article, we have discussed about Java Program to Print ‘Hello World’ n times by Using Recursion

In this program we are going to see how to add all the numbers from 1 to n by using recursion by using Java programming language.

Java Program to Add All the Numbers from 1 to n by Using Recursion

Now let’s see different ways to add All the Numbers from 1 to n by Using Recursion.

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

Method-1: Java Program to Add All the Numbers from 1 to n By Using Static Input and Recursion

Approach:

Declare and initiate two static integer variables say count and sum with the value of 0.
Declare an integer variable n and assign any value to it.
Then call a user defined method calculateValue() and pass n as parameter.
Inside the user defined method add the value of updated count value into sum variable by using an If statement.
Call the same method inside that user defined method recursively.
Print the result.

Program:

class Main
{
    //Declare and initiate two static integer variables say count and sum with the value as 0. 
    static int count=0,sum=0;
    public static void main(String[] args)
    {
        int n=20;
        //calling the method
        calculateValue(n);
        System.out.print("sum of all number from 1 to "+n+" is= "+sum);
    }
    
    //define the method
    public static void calculateValue(int n)
    {
        //Increase the value of count by 1
        count++;
        //Check the condition whether the value of count is continuing till the target value reaches.
        if(count<=n)
        {
            //calculate the result
            sum=sum+count;
            //call the same function inside this user defined method recursively
            calculateValue(n);
        }
    }
}

Output:

sum of all number from 1 to 20 is= 210

Method-2: Java Program to Add All the Numbers from 1 to n By Using User Input and Recursion

Approach:

Declare and initiate two static integer variables say count and sum with the value of 0.
Declare an integer variable n and prompt the user to enter value for it by using Scanner class.
Then call a user defined method calculateValue() and pass n as parameter.
Inside the user defined method add the value of updated count value into sum variable by using an If statement.
Call the same method inside that user defined method recursively.
Print the result.

Program:

import java.util.Scanner;
class Main
{
    //Declare and initiate two static integer variable say count and sum with the value of 0. 
    static int count=0,sum=0;
    public static void main(String[] args)
    {
        //create object of scanner class.
        Scanner sc=new Scanner(System.in);
        System.out.print("Enter the value of n= ");
        //prompt the user to enter the value
        int n=sc.nextInt();
        //calling the method
        calculateValue(n);
        System.out.print("sum of all number from 1 to "+n+" is= "+sum);

    }
    
    //define the method
    public static void calculateValue(int n)
    {
        //Increase the value of count by 1
        count++;
        //Check the condition whether the value of count is continuing till the value reaches.
        if(count<=n)
        {
            //calculate the result
            sum=sum+count;
            //call the same function inside this user defined method recursively
            calculateValue(n);
        }
    }
}

Output:

Enter the value of n= 30
sum of all number from 1 to 30 is= 465

Guys who are serious about learning the concepts of the java programming language should practice this list of programs in java and get a good grip on it for better results in exams or interviews.

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