实现了隐形耦合，help输出内容与help的输出函数无关，使得新的命令加入的时候，help能自动输出新的内容。
添加了新元素：添加了简单的故事场景。
城堡游戏演示：

代码如下：

Game.java

城堡游戏的主函数

package castle;

import java.util.ArrayList;
import java.util.HashMap;
import java.util.Scanner;

public class Game {
    private Room currentRoom;
    private HashMap<String, Handler> handlers = new HashMap<String, Handler>();
    protected ArrayList<String> cmds = new ArrayList<String>();
    public Game() 
    {
// handlers.put("go", new HandlerGo());
    	handlers.put("bye", new HandlerBye(this));
    	handlers.put("help", new HandlerHelp(this));
    	handlers.put("go", new HandlerGo(this));
    	for (String cmd : handlers.keySet()) {
    		cmds.add(cmd);
    	}
        createRooms();
    }

    private void createRooms()
    {
        Room outside, lobby, pub, study, bedroom, inside, bedroomup;
      
        // 制造房间
        
        outside = new Room("城堡外");
        inside = new Room("城堡内");
        lobby = new Room("大堂");
        pub = new Room("小酒吧");
        study = new Room("书房");
        bedroom = new Room("卧室");
        bedroomup = new Room("卧室二楼");
// hoteldown = new Room("宾馆一楼");
// hotelup = new Room("宾馆二楼");
        // 设置房间故事
        outside.setNarration("城堡外","恭喜你逃出了城堡");
        inside.setNarration("城堡内", "你现在在城堡的一个恐怖黑暗的广场上");
        lobby.setNarration("大堂", "你来到了城堡的大堂，大堂里面有着恐怖的石像");
        pub.setNarration("小酒吧", "这是一间幽深的酒吧，傍边到处是黑色的酒瓶，还有这恐怖的音乐在播放着");
        study.setNarration("书房", "这是城堡的书房，里面记载着这个城堡的过去");
        bedroom.setNarration("卧室", "你来到了城堡主人的卧室，这里是最黑暗的地方，你的心跳跳的越来越快，快点离开这里吧！");
        bedroomup.setNarration("卧室二楼", "恭喜你来到了城堡主人的卧室二楼，并且发现了一个箱子，你打开箱子后找到了钥匙，请拿着钥匙快速逃出城堡吧！");
        
        // 初始化房间的出口
        outside.setExit("south", inside);
        inside.setExit("north", outside);
        inside.setExit("east", lobby);
        inside.setExit("south", study);
        inside.setExit("west", pub); 
        lobby.setExit("west", inside);
        pub.setExit("east", inside);
        study.setExit("north", inside);
        study.setExit("east", bedroom);
        bedroom.setExit("west", study);
        bedroom.setExit("up", bedroomup);
        bedroomup.setExit("down", bedroom);
        
        currentRoom = inside;  // 从城堡门外开始
    }
    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。任务：你需要在城堡内找到宝箱钥匙并带到城堡外去。");
        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 showPrompt() {
		 String currentnarration = currentRoom.getNarration(currentRoom.toString());
		 System.out.println("你在" + currentRoom + "\n场景描述：" + currentnarration);
         System.out.print("出口有: ");
         System.out.print(currentRoom.getExitDesc());
         System.out.println();
	}
	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;
	 			}
	 		}
		}
		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！");
	}

}

Room.java

城堡游戏中的房间模块

package castle;

import java.util.HashMap;

public class Room {
    private String description;
    private HashMap<String, Room> exits = new HashMap<String, Room>();
    private HashMap<String, String> narration = new HashMap<String, String>();
    
    public Room(String description) 
    {
        this.description = description;
    }
    public void setExit(String dir, Room room) {
    	exits.put(dir, room);
    }
    public void setNarration(String room, String narr) {
    	narration.put(room, narr);
    }
    @Override
    public String toString()
    {	
        return description;
    }
    public String getExitDesc() {
    	StringBuffer sb = new StringBuffer();
    	for (String dir : exits.keySet()) {
    		sb.append(dir);
    		sb.append(' ');
    	}
    		return sb.toString();
    }
    public Room getExit(String direction) {
    	return exits.get(direction);
    }
    public String getNarration(String direction) {
    	return narration.get(direction);
    }
}

Handler.java

城堡游戏中的添加各种功能的父类模块

package castle;

public class Handler {
	protected Game game;
	
	public Handler(Game game) {
		this.game = game;
	}
	public void doCmd(String word) {}
	public boolean isBye() {return false;}
}

HandlerBye.java

功能模块的子类实现结束功能

package castle;

public class HandlerBye extends Handler{
	public HandlerBye(Game game) {
		super(game);
	}
	@Override
	public boolean isBye() {
		return true;
	}
}

HandlerHelp.java

功能模块的子类实现帮助功能

package castle;

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：" + game.cmds);
		
        System.out.println("如：\tgo east");
	}
	
}

HandlerGo.java

功能模块的子类实现go功能

package castle;

public class HandlerGo extends Handler {
	public HandlerGo(Game game) {
		super(game);
	}
	@Override
	public void doCmd(String word) {
		game.goRoom(word);
	}

}

学习心得：

• 消除代码复制

  • 提取出来，改为函数。

• 增加可扩展性

  • 可以运行的代码 != 良好的代码
  • 对代码做维护的时候最能看出代码的质量

• 用封装来降低耦合

• Sring每次都String做+时，都会产生新的对象，系统开销较大。

• StringBuffer是可以不断修改的对象。

  • StringBuffer sb = new StringBuffer();
  • sb.append(“haha”);