Java Program to find Sum of Natural Numbers

The positive integers 1, 2, 3, 4 etc. are known as natural numbers. Here we will see three programs to calculate and display the sum of natural numbers.

• First Program calculates the sum using while loop
• Second Program calculates the sum using for loop
• Third Program takes the value of n(entered by user) and calculates the sum of n natural numbers

To understand these programs you should be familiar with the following concepts of Core Java Tutorial:

• Java For loop
• Java While loop

Example 1: Program to find the sum of natural numbers using while loop

public class Demo {

    public static void main(String[] args) {

       int num = 10, count = 1, total = 0;

       while(count <= num)
       {
           total = total + count;
           count++;
       }

       System.out.println("Sum of first 10 natural numbers is: "+total);
    }
}

Output:

Sum of first 10 natural numbers is: 55

Example 2: Program to calculate the sum of natural numbers using for loop

public class Demo {

    public static void main(String[] args) {

       int num = 10, count, total = 0;

       for(count = 1; count <= num; count++){
           total = total + count;
       }

       System.out.println("Sum of first 10 natural numbers is: "+total);
    }
}

Output:

Sum of first 10 natural numbers is: 55

Example 3: Program to find sum of first n (entered by user) natural numbers

import java.util.Scanner;
public class Demo {

    public static void main(String[] args) {

        int num, count, total = 0;

        
        System.out.println("Enter the value of n:");
        //Scanner is used for reading user input
        Scanner scan = new Scanner(System.in);
        //nextInt() method reads integer entered by user
        num = scan.nextInt();
        //closing scanner after use
        scan.close();
        for(count = 1; count <= num; count++){
            total = total + count;
        }

        System.out.println("Sum of first "+num+" natural numbers is: "+total);
    }
}

Output:

Enter the value of n:
20
Sum of first 20 natural numbers is: 210