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Java Program to Calculate the Sum of Natural Numbers

To understand this example, you should have the knowledge of the following Java programming topics:

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 SumNatural {

    public static void main(String[] args) {

        int num = 100, sum = 0;

        for(int i = 1; i <= num; ++i)
        {
            // sum = sum + i;
            sum += i;
        }

        System.out.println("Sum = " + sum);
    }
}

Output


              

Sum = 5050

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

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

Example 2: Sum of Natural Numbers using while loop


              

public class SumNatural {

    public static void main(String[] args) {

        int num = 50, i = 1, sum = 0;

        while(i <= num)
        {
            sum += i;
            i++;
        }

        System.out.println("Sum = " + sum);
    }
}

Output


              

Sum = 1275

In the above program, unlike a for loop, we have to increment the value of i inside the body of the loop.

Though both programs are technically correct, it is better to use for loop in this case. It’s because the number of iteration (up to num) is known.

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