Java Program to Find Factorial of a Number

📘 What is a Factorial?

The factorial of a number n (written as n!) is the product of all positive integers less than or equal to n.

[
n! = n × (n-1) × (n-2) × … × 1
]

For example:

• 5! = 5 × 4 × 3 × 2 × 1 = 120

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🧩 Java Code:

// Java program to find factorial of a number

import java.util.Scanner;

public class Factorial {
    public static void main(String[] args) {

        // Create Scanner object to take input
        Scanner sc = new Scanner(System.in);

        // Take number as input from user
        System.out.print("Enter a number: ");
        int num = sc.nextInt();

        // Initialize factorial variable
        long fact = 1;

        // Loop to multiply numbers from 1 to num
        for (int i = 1; i <= num; i++) {
            fact = fact * i;
        }

        // Display the result
        System.out.println("Factorial of " + num + " is: " + fact);

        // Close scanner
        sc.close();
    }
}

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🧠 Explanation:

Step	Description
1️⃣	Import the Scanner class to take user input.
2️⃣	Read an integer number from the user.
3️⃣	Initialize a variable fact = 1 to store the factorial value.
4️⃣	Use a for loop from 1 to the given number and multiply each value to fact.
5️⃣	Finally, print the factorial result.

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💻 Sample Output:

Enter a number: 5
Factorial of 5 is: 120

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⚙️ Alternative (Using Recursion)

// Factorial using recursion
import java.util.Scanner;

public class RecursiveFactorial {
    static long factorial(int n) {
        if (n == 0 || n == 1)
            return 1;
        else
            return n * factorial(n - 1);
    }

    public static void main(String[] args) {
        Scanner sc = new Scanner(System.in);
        System.out.print("Enter a number: ");
        int num = sc.nextInt();
        System.out.println("Factorial of " + num + " is: " + factorial(num));
        sc.close();
    }
}