Java Programs

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Operators & Expressions

Java Program: Product of First N Natural Numbers

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

 
INPUT :
Enter the value of N: 5

OUTPUT :
Product of first 5 natural numbers is: 120
 

Explanation

✔ 1. What Does the Program Do?

It calculates:

1 × 2 × 3 × ... × N

This is called factorial.

✔ 2. Logic Used

long product = 1;

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

    product *= i;

}

• Starts multiplication from 1
• Multiplies each number up to N
• Uses long to handle large results

✔ 3. Step-by-Step Example (N = 5)

1 × 2 = 2

2 × 3 = 6

6 × 4 = 24

24 × 5 = 120

✔ 4. Program Flow

1. Accept value of N
2. Initialize product = 1
3. Multiply numbers from 1 to N
4. Display final result