Factorial.java Source code

Introduction

Here is the source code for Factorial.java

Source

//package numeric;

/**
* This class calculates the Factorial of a
* numbers passed into the program through
* command line arguments.
*
* @author Alex Laird
* @version 1.0
* File: Factorial.java
* Created: Sep 2008
*/
public class Factorial {
    /**
    * Returns the Factorial of a number that
    * is passed into the method through command
    * line arguments.
    *
    * @param a The counting variable and initial condition for the Factorial.
    * @param factorial The running value of the Factorial.
    * @throws NegativeNumberException if the input given is negative.
    * @returns the calculated Factorial.
    */
    public static double calcFactorial(int a) throws Exception {
        double factorial = a;

        // throw an exception if the input is negative
        if (a < 0) {
            throw new Exception("The user has entered a " + "negative number.");
        }

        for (int i = (a - 1); i > 1; i--)
            factorial *= i;

        return factorial;
    }

    /**
    * The main method from which the program executes;
    * it handles all I/O and method execution.
    *
    * @param args Arguments received from the command line (one number).
    * @param factorial The calculated Factorial of args[0].
    */
    public static void main(String[] args) {
        // ensure the user only enters one argument
        if (args.length == 1) {
            // ensure the users argument is a number
            try {
                // calculate factorial
                double factorial = calcFactorial(Integer.parseInt(args[0]));

                System.out.println("The Factorial of " + args[0] + " is " + factorial + ".");
            } catch (NumberFormatException c) {
                System.out.println("Your argument must be in " + "the form of an integer when "
                        + "running the program (ex. " + "enter 'java numeric." + "Factorial 5').");
            } catch (Exception c) {
                // used only in GUI
            }
        } else {
            System.out.println("Enter one number as an argument " + "when running the program (ex. "
                    + "enter 'java numeric.Factorial 5').");
        }
    }
}