设计原则之城堡游戏（上）

这是一个简单的空间游戏

Game类

public class Game {
    private Room currentRoom;
    private HashMap<String, Handler> handlers = new HashMap<String, Handler>();

    public Game()
    {
        handlers.put("go", new HandlerGo(this));
        handlers.put("bye", new HandlerBye(this));
        handlers.put("help", new HandlerHelp(this));
        createRooms();
    }

    private void createRooms()
    {
        Room outside;
        Room lobby;
        Room pub;
        Room study;
        Room bedroom;

        //    制造房间
        outside = new Room("城堡外");
        lobby = new Room("大堂");
        pub = new Room("小酒吧");
        study = new Room("书房");
        bedroom = new Room("卧室");

        //  初始化房间的出口
        outside.setExit("east", lobby);
        outside.setExit("south", study);
        outside.setExit("west", pub);
        lobby.setExit("west", outside);
        pub.setExit("east", outside);
        study.setExit("north", outside);
        study.setExit("east", bedroom);
        bedroom.setExit("west", study);
        lobby.setExit("up", pub);
        pub.setExit("down", lobby);
        currentRoom = outside;  //    从城堡门外开始
    }

    public void showPrompt() {
        System.out.println("你在" + currentRoom);
        System.out.print("出口有: ");
        System.out.print(currentRoom.getExitDesc());
        System.out.println();
    }

    private void printWelcome() {
        System.out.println();
        System.out.println("欢迎来到城堡！");
        System.out.println("这是一个超级无聊的游戏。");
        System.out.println("如果需要帮助，请输入 'help' 。");
        System.out.println();
        showPrompt();
    }

    // 以下为用户命令

    public void goRoom(String direction)
    {
        Room nextRoom = currentRoom.getExit(direction);
        if (nextRoom == null) {
            System.out.println("那里没有门！");
        }
        else {
            currentRoom = nextRoom;
            showPrompt();
        }
    }

    public void play() {
        Scanner in = new Scanner(System.in);
        while ( true ) {
            String line = in.nextLine();
            String[] words = line.split(" ");
            Handler handler = handlers.get(words[0]);
            String value = "";
            if ( words.length > 1 )
                value = words[1];
            if ( handler != null ) {
                handler.doCmd(value);
                if ( handler.isBye() )
                    break;
            }
//            if ( words[0].equals("help") ) {
//                printHelp();
//            } else if (words[0].equals("go") ) {
//                goRoom(words[1]);
//            } else if ( words[0].equals("bye") ) {
//                break;
//            }
        }
        in.close();
    }

    public static void main(String[] args) {
        Game game = new Game();
        game.printWelcome();
        game.play();
        System.out.println("感谢您的光临。再见！");
    }

}

• 消除代码复制的两个手段就是函数和父类。
  if-else是一种硬编码，转换为框架。