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:

## 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

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