2021-09-29

外观模式为子系统中的一组接口提供一个一致的界面，此模式定义了一个高层接口，这个接口使得这一子系统更加容易使用。
外观模式通过定义一个一致的接口，用以屏蔽内部子系统的细节，使得调用端只需跟这个接口发生调用，而无需关心这个子系统的内部细节。

说明：
（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的子系统对象
（2）调用者（Client）：外观接口的调用者
（3）子系统：处理Facade对象指派的任务，功能的实际提供者

DVDPlayer.java

public class DVDPlayer {
	
	// 单例模式（饿汉式）
	// 1.私有化构造器
	private DVDPlayer() {
		
	}
	
	// 2.类的内部创建对象
	private static DVDPlayer instance = new DVDPlayer();
	
	// 3. 提供公共的静态方法，返回实例对象
	public static DVDPlayer getInstance() {
		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. ");
	}
}

Popcorn.java

public class Popcorn {

	// 单例模式（饿汉式）
	// 1.私有化构造器
	private Popcorn() {

	}

	// 2.类的内部创建对象
	private static Popcorn instance = new Popcorn();

	// 3. 提供公共的静态方法，返回实例对象
	public static Popcorn getInstance() {
		return instance;
	}

	public void on() {
		System.out.println(" Popcorn on. ");
	}

	public void off() {
		System.out.println(" Popcorn off. ");
	}

	public void pop() {
		System.out.println(" Popcorn is poping. ");
	}

}

Projector.java

public class Projector {

	// 单例模式（饿汉式）
	// 1.私有化构造器
	private Projector() {

	}

	// 2.类的内部创建对象
	private static Projector instance = new Projector();

	// 3. 提供公共的静态方法，返回实例对象
	public static Projector getInstance() {
		return instance;
	}

	public void on() {
		System.out.println(" Projector on. ");
	}

	public void off() {
		System.out.println(" Projector off. ");
	}

	public void facus() {
		System.out.println(" Projector is facusing. ");
	}

}

Screen.java

public class Screen {

	// 单例模式（饿汉式）
	// 1.私有化构造器
	private Screen() {
		
	}
	
	// 2.类的内部创建对象
	private static Screen instance = new Screen();
	
	// 3. 提供公共的静态方法，返回实例对象
	public static Screen getInstance() {
		return instance;
	}

	public void up() {
		System.out.println(" Screen up. ");
	}
	
	public void down() {
		System.out.println(" Screen down. ");
	}
}

Stereo.java

public class Stereo {

	// 单例模式（饿汉式）
	// 1.私有化构造器
	private Stereo() {

	}

	// 2.类的内部创建对象
	private static Stereo instance = new Stereo();

	// 3. 提供公共的静态方法，返回实例对象
	public static Stereo getInstance() {
		return instance;
	}

	public void on() {
		System.out.println(" Stereo on. ");
	}

	public void off() {
		System.out.println(" Stereo off. ");
	}

	public void up() {
		System.out.println(" Stereo up. ");
	}
	
	public void down() {
		System.out.println(" Stereo down. ");
	}

}

TheaterLight.java

public class TheaterLight {

	// 单例模式（饿汉式）
	// 1.私有化构造器
	private TheaterLight() {

	}

	// 2.类的内部创建对象
	private static TheaterLight instance = new TheaterLight();

	// 3. 提供公共的静态方法，返回实例对象
	public static TheaterLight getInstance() {
		return instance;
	}

	public void on() {
		System.out.println(" TheaterLight on. ");
	}

	public void off() {
		System.out.println(" TheaterLight off. ");
	}

	public void dim() {
		System.out.println(" TheaterLight dim. ");
	}

	public void bright() {
		System.out.println(" TheaterLight bright. ");
	}

}

HomeTheaterFacade.java

public class HomeTheaterFacade {
	
	// 定义各个子系统的对象
	private DVDPlayer dvdPlayer;
	private Popcorn popcorn;
	private Projector projector;
	private Screen screen;
	private Stereo stereo;
	private TheaterLight theaterLight;
	
	// 构造器
	public HomeTheaterFacade() {
		super();
		this.dvdPlayer = DVDPlayer.getInstance();
		this.popcorn = Popcorn.getInstance();
		this.projector = Projector.getInstance();
		this.screen = Screen.getInstance();
		this.stereo = Stereo.getInstance();
		this.theaterLight = TheaterLight.getInstance();
	}
	
	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();
	}
}

Client.java

public class Client {

	public static void main(String[] args) {
		
		HomeTheaterFacade homeTheaterFacade = new HomeTheaterFacade();
		
		homeTheaterFacade.ready();
		
		System.out.println("**********");
		
		homeTheaterFacade.play();
		
		System.out.println("**********");
		
		homeTheaterFacade.pause();
		
		System.out.println("**********");
		
		homeTheaterFacade.end();
		
	}