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

Prerequisite: Recursion in Java

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.

### 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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