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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