JAVA program to find sum of first n natural numbers

JAVA program to find sum of first n natural numbers

This JAVA program is to find the sum of first n natural numbers. Natural numbers are non-negative integers.

For example if we take 3 natural numbers 1,2,3 then their sum=6

Logic

Take a for loop starting with 0 keep incrementing the value of i and add it to the previous value.

Dry Run of the Program

Take input ‘n’ .Let us take n=3  //So it will give summation of 4 natural numbers

1st iteration   for(i=0;i<=n;i++) i.e.  for(i=0;i<=3;i++)

sum=sum+i    i.e sum = 0 + 0  hence sum=0

2nd iteration   for(i=1;i<=n;i++) i.e.  for(i=1;i<=3;i++)

sum=sum+i    i.e sum = 0 + 1  hence sum=1

3rd iteration   for(i=2;i<=n;i++) i.e.  for(i=2;i<=3;i++)

sum=sum+i    i.e sum = 1 + 2 hence sum=3

4th iteration   for(i=3;i<=n;i++) i.e.  for(i=3;i<=3;i++)

sum=sum+i    i.e sum = 3 + 3  hence sum=6

So output we get as sum = 6 for n=3.

Program

import java.util.*;

class sum {
    public static void main(String[] args) {
        Scanner sc = new Scanner(System.in);
        System.out.println("Enter a no");
        int n = sc.nextInt();
        int i,sum=0;
	
	for(i=0;i<=n;i++)
	{
		sum = sum + i;
	}  

 	System.out.println("Sum of first "+n+" natural nos = "+sum);
    }
}

Output

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