Java Program to Find Factorial of a Number

WAP to find the factorial of a number in Java

What are Factorial Numbers:

A factorial number is the product of all positive integers from 1 to that number.
It is written as n! (n factorial).
Examples:
- 5! = 5 x 4 x 3 x 2 x 1 = 120
- 3! = 3 x 2 x 1 = 6
- 1! = 1

Logical Steps:

To find the factorial of a number, follow these steps:
1. Take a number.
2. Use a variable (fact) initialized to 1 to store the result.
3. Use a Loop to Calculate Factorial:
  - Use a for loop starting from 1 to the given number (n).
  - Multiply the fact variable by the loop counter in each iteration.
4. Print the value of fact after the loop completes.

Program:

Below is the simple program:

public class FactorialProgram
{
    public static void main(String[] args)
    {
        int no = 5;

        if (no < 0)
        {
            System.out.println("Factorial is not defined for negative numbers.");
        }
        else
        {
            long fact = 1;  // Variable to store the factorial result

            // Calculate factorial using a loop
            for (int i = 1; i <= no; i++)
            {
                fact = fact * i;
            }

            // Display the result
            System.out.println("Factorial of " + no + " is: " + fact);
        }
    }
}

Output:

Factorial of 5 is: 120

Below is the program by taking user input:

import java.util.Scanner;

public class FactorialProgram
{
    public static void main(String[] args)
    {
        Scanner scanner = new Scanner(System.in);

        // Prompt the user to enter a number
        System.out.print("Enter a number to find its factorial: ");
        int no = scanner.nextInt();

        if (no < 0)
        {
            System.out.println("Factorial is not defined for negative numbers.");
        }
        else
        {
            long fact = 1;  // Variable to store the factorial result

            // Calculate factorial using a loop
            for (int i = 1; i <= no; i++)
            {
                fact = fact * i;
            }

            // Display the result
            System.out.println("Factorial of " + no + " is: " + fact);
        }

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

Output:

Enter a number to find its factorial: 6
Factorial of 6 is: 720

Program Explanation:

Import Scanner Class:
- The Scanner class is imported to take user input.
Declare a Variable:
- An integer variable (no) is declared to store the user’s input.
Take Input:
- The program prompts the user to enter a number to find the factorial number.
- scanner.nextInt() is used to read and store the input in the no variable.
Check for Valid Input:
- If n is less than 0, the program displays an error message (factorial is not defined for negative numbers).
Use a for Loop to Calculate Factorial:
- The loop iterates from 1 to no. In each iteration, the fact variable is multiplied by the loop counter (i).
- The result is stored back in fact.
Display the Result:
- After the loop, the value of fact is printed as the factorial of the given number.
Close Scanner:
- The scanner.close() method is used to close the input stream and release resources.

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WAP to find the factorial of a number in Java

What are Factorial Numbers:

Logical Steps:

Program:

Output:

Output:

Program Explanation:

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