设计原则之城堡游戏（下）

制造Handler类（框架+数据）以及它的子类来加强可扩展性

• 命令的解析脱离if-else

• 定义一个Handler来处理命令

• 用Hash表来保存命令和Handler之间的关系

Handler类及其子类

public class Handler {
    protected Game game;

    public Handler(Game game) {
        this.game = game;
    }

    public void doCmd(String word) {    //cmd=command
    }
    public boolean isBye() {
        return false;
    }
}

public class HandlerBye extends Handler {
    public HandlerBye(Game game) {
        super(game);
    }

    @Override
    public boolean isBye() {
        return true;
    }
}

public class HandlerGo extends Handler {
    public HandlerGo(Game game) {
        super(game);
    }

    @Override
    public void doCmd(String word) {
        game.goRoom(word);
    }
}

public class HandlerHelp extends Handler {
    public HandlerHelp(Game game) {
        super(game);
    }

    @Override
    public void doCmd(String word) {
        System.out.println("迷路了吗？你可以做的命令有：go bye help");
        System.out.println("如：\tgo east");
    }
}