/* * Copyright (c) 2000 David Flanagan.  All rights reserved. * This code is from the book Java Examples in a Nutshell, 2nd Edition. * It is provided AS-IS, WITHOUT ANY WARRANTY either expressed or implied. * You may study, use, and modify it for any non-commercial purpose. * You may distribute it non-commercially as long as you retain this notice. * For a commercial use license, or to purchase the book (recommended), * visit http://www.davidflanagan.com/javaexamples2. */package com.davidflanagan.examples.basics;/** * This program computes and displays the factorial of a number specified * on the command line.  It handles possible user input errors with try/catch. **/public class FactComputer {    public static void main(String[] args) {        // Try to compute a factorial.	// If something goes wrong, handle it in the catch clause below.        try {            int x = Integer.parseInt(args[0]);            System.out.println(x + "! = " + Factorial4.factorial(x));        }        // The user forgot to specify an argument.	// Thrown if args[0] is undefined.        catch (ArrayIndexOutOfBoundsException e) {            System.out.println("You must specify an argument");            System.out.println("Usage: java FactComputer <number>");        }        // The argument is not a number.  Thrown by Integer.parseInt().        catch (NumberFormatException e) {            System.out.println("The argument you specify must be an integer");        }        // The argument is < 0.  Thrown by Factorial4.factorial()        catch (IllegalArgumentException e) {            // Display the message sent by the factorial() method:            System.out.println("Bad argument: " + e.getMessage());        }    }}