基于Java的软件信息系统－项目管理

				package cmd;								import core.*;								public class UnknownCommand extends SimpleCommand				{				    public void executeCommand ()				    { 				        System.out.println ("Unknown command. Use 'help' to see options.");				    }				    public String getMenuName ()				    { return "_unknown"; }				    public String getName ()				    { return "_unknown"; }				    public String getDescription ()				    { return "Error: Unknown command"; }				    public Command makeInstance ()				    { return new UnknownCommand (); }				}