help.java

用command模式写的一个简单的java 程序

/******************************************************************************
*  Filename    :help.java
*  Description :The help command displays help for FileSystemShell. If the user types
*               help [command]
*               help invokes that command's help method.
*
*  Author      :xunzy
*
*  History     :2004-02-16   Created
******************************************************************************/

import java.lang.reflect.Method;
import java.io.*;
import java.util.Vector;


public class help implements Command {
    public void execute(File currentDir, Vector args) 
        throws CommandException {
        
        if (args.isEmpty())
            help();
        else {
            String commandName = (String)args.firstElement();
            Command command = FileSystemShell.loadCommand(commandName);
            if (command != null)
                command.help();
            else 
                throw new CommandException(new Exception(), 
                    "No help available for this command");
        }
    }
    
    public void help() { System.out.print("Usage: help [command]"); }
}