Java Programs

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Operators & Expressions

Java Program: Sum of first N Natural Numbers

import java.util.Scanner;
 
public class SumOfNaturalNumbers {
    public static void main(String[] args) {
 
        Scanner sc = new Scanner(System.in);
 
        System.out.print("Enter the value of N: ");
        int n = sc.nextInt();
 
        int sum = 0;
 
        // Loop to calculate sum
        for (int i = 1; i <= n; i++) {
            sum += i;
        }
 
        System.out.println("\nSum of first " + n + " natural numbers is: " + sum);
 
        sc.close();
    }
}

 
INPUT :
Enter the value of N: 10

OUTPUT :
Sum of first 10 natural numbers is: 55
 

Explanation

✔ 1. What are Natural Numbers?

Natural numbers are positive integers starting from 1:
1, 2, 3, 4, 5, ...

✔ 2. Logic Used

The program uses a for loop:

for (int i = 1; i <= n; i++) {

    sum += i;

}

This adds each number from 1 to N to the variable sum.

✔ 3. Step-by-Step Example (N = 5)

1 + 2 + 3 + 4 + 5 = 15

✔ 4. Program Flow

1. Read the value of N
2. Initialize sum to 0
3. Loop from 1 to N and add values
4. Display the final sum

✅ Alternative Formula Method

You can also compute directly using:

Sum=n(n+1)/2