Program to find the sum of first n natural numbers

Given problem statment

During the final skill exam teacher was given a problem and asked everyone to write the algorithm to it, and also advised that try to implement a different approach from others

Question: Write an algorithm to calculate sum of first ‘n’ natural numbers

Methods to solve the problem

The simple solution is to intialize result as 0 and implement a for loop to increment the result.

A more elegant solution is to use the formula (n * (n + 1))/2

Java program to find the sum of first n natural numbers using for loop

class sum {
    public static void main(String[] args) {
        int sum = sumOfNNaturalNums(6);
        System.out.println("sum is = " + sum);
    }

    public static int sumOfNNaturalNums(int n) {
        int result = 0;
        for (int i = 1; i <= n; i++) {
            result += i;
        }
        return result;
    }
}

Java program to find the sum of first n natural numbers using formula

class sum {
    public static void main(String[] args) {
        int sum = sumOfNNaturalNumsUsingFormula(6);
        System.out.println("sum is = " + sum);
    }

    public static int sumOfNNaturalNumsUsingFormula(int n) {
        return n * (n + 1) / 2;
    }
}

Output

Output of the program when the input is 6 is 21