一、基本介绍

二、UML类图

1. 外观类（Facade）：为调用端提供统一的调用接口，外观类知道哪些子系统负责处理请求，从而将调用端的请求代理给适当子系统对下那个
2. 调用者（Client）:外观接口的调用者

3. 子系统的集合：指模块或者子系统，处理Facade对象指派的任务，他是功能的提供者

   三、代码

   DVD类

   public class DVDPlayer {
    //使用单例模式, 使用饿汉式
    private static DVDPlayer instance = new DVDPlayer();
    public static DVDPlayer getInstanc() {
        return instance;
    }
    public void on() {
        System.out.println(" dvd on ");
    }
    public void off() {
        System.out.println(" dvd off ");
    }
    public void play() {
        System.out.println(" dvd is playing ");
    }
    //....
    public void pause() {
        System.out.println(" dvd pause ..");
    }
   }

   爆米花类

   public class Popcorn {
    private static Popcorn instance = new Popcorn();
    public static Popcorn getInstance() {
        return instance;
    }
    public void on() {
        System.out.println(" popcorn on ");
    }
    public void off() {
        System.out.println(" popcorn ff ");
    }
    public void pop() {
        System.out.println(" popcorn is poping  ");
    }
   }

   投影仪类

   public class Projector {
    private static Projector instance = new Projector();
    public static Projector getInstance() {
        return instance;
    }
    public void on() {
        System.out.println(" Projector on ");
    }
    public void off() {
        System.out.println(" Projector ff ");
    }
    public void focus() {
        System.out.println(" Projector is Projector  ");
    }
    //...
   }

   外观类

   ```java public class HomeTheaterFacade {

   //定义各个子系统对象 private TheaterLight theaterLight; private Popcorn popcorn; private Stereo stereo; private Projector projector; private Screen screen; private DVDPlayer dVDPlayer;

//构造器
public HomeTheaterFacade() {
    super();
    this.theaterLight = TheaterLight.getInstance();
    this.popcorn = Popcorn.getInstance();
    this.stereo = Stereo.getInstance();
    this.projector = Projector.getInstance();
    this.screen = Screen.getInstance();
    this.dVDPlayer = DVDPlayer.getInstanc();
}
//操作分成 4 步
public void ready() {
    popcorn.on();
    popcorn.pop();
    screen.down();
    projector.on();
    stereo.on();
    dVDPlayer.on();
    theaterLight.dim();
}
public void play() {
    dVDPlayer.play();
}
public void pause() {
    dVDPlayer.pause();
}
public void end() {
    popcorn.off();
    theaterLight.bright();
    screen.up();
    projector.off();
    stereo.off();
    dVDPlayer.off();
}

}

<a name="SJ8Kx"></a>
#### 客户端测试
```java
public class Client {
    public static void main(String[] args) {
        // TODO Auto-generated method stub
        //这里直接调用。。 很麻烦
        HomeTheaterFacade homeTheaterFacade = new HomeTheaterFacade();
        homeTheaterFacade.ready();
        homeTheaterFacade.play();
        homeTheaterFacade.end();
    }
}

四、注意事项