The positive numbers 1, 2, 3... are known as natural numbers and its sum is the result of all numbers starting from 1 to the given number.

For n, the sum of natural numbers is:

1 + 2 + 3 + ... + n

Example 1: Sum of Natural Numbers using for loop

public class NaturalNumbers public static void main(String[] args) { int num = 100, sum = 0; for(int i = 1; i <= num; ++i) System.out.println("Sum = " + sum); } |

When you run the program, the output will be:

`Sum = 5050`

The above program loops from 1 to the given `num`(100) and adds all numbers to the variable `sum`.

We can solve this problem using a while loop as follows:

**Example 2:** Sum of Natural Numbers using while loop

public class NaturalNumbers public static void main(String[] args) { int num = 75, i = 1, sum = 0; while(i <= num) System.out.println("Sum = " + sum); } |

output will be:

`Sum = 2850`