Calculate Factorial of a Given Number in Java

This program calculates the factorial of a given number using recursion in Java. The factorial of a number n is the product of all positive integers less than or equal to n. It is denoted by n! and is defined as:

n! = n * (n - 1) * (n - 2) * ... * 1

For example:

• 5! = 5 * 4 * 3 * 2 * 1 = 120
• 3! = 3 * 2 * 1 = 6
• 0! = 1 (by definition)

Java Program

/**
 * This class contains a method to calculate the factorial of a given number.
 */
public class FactorialCalculator {

    /**
     * This method calculates the factorial of a given number using recursion.
     * @param n The number for which the factorial is to be calculated. Must be a non-negative integer.
     * @return The factorial of the given number.
     */
    public static long factorial(int n) {
        // Base case: factorial of 0 is 1
        if (n == 0) {
            return 1;
        }
        // Recursive case: n! = n * (n - 1)!
        return n * factorial(n - 1);
    }

    public static void main(String[] args) {
        // Example usage of the factorial method
        int number = 5;
        long result = factorial(number);
        System.out.println("The factorial of " + number + " is " + result);
    }
}

Explanation

The program consists of the following parts:

• FactorialCalculator Class: This class contains the method to calculate the factorial.
  • factorial(int n): This method is a recursive function that calculates the factorial of a given number. It has one parameter n, which is the number for which the factorial is to be calculated.
  • main(String[] args): This is the main method where the program execution begins. It calls the factorial method and prints the result.
• factorial Method: This method uses recursion to calculate the factorial.
  • Base Case: If n is 0, the method returns 1, because by definition, 0! = 1.
  • Recursive Case: If n is greater than 0, the method returns n multiplied by the factorial of n - 1 (n! = n * (n - 1)!).

How to Run the Program

To run this program, follow these steps:

1. 1. Save the code to a file named FactorialCalculator.java.
   2. Open a terminal and navigate to the directory containing the file.
   3. Compile the program using the following command:

javac FactorialCalculator.java

1. 1. Run the compiled program using the following command:

java FactorialCalculator

The program will output the factorial of the number specified in the main method.