设计模式读书笔记-外观模式
外观模式提供了一个统一的接口,用来访问子系统中的一群接口.让子系统更容易使用.主要应用了OO设计原则中的最少知识原则,减少对象间的交互,只和你有关的人交谈;降低耦合;
我们看一个家庭影院的例子,监听影院系统，只需要暴露几个用户关心的方法，看电影，结束电影，其他的影院设备控制不需要跑路给用户，采用外观模式，将将这个子系统封装一个外观.
代码如下：
家庭影院外观类：
public class HomeTheaterFacade {
Amplifier amp;
Tuner tuner;
DvdPlayer dvd;
CdPlayer cd;
Projector projector;
TheaterLights lights;
Screen screen;
PopcornPopper popper;
public HomeTheaterFacade(Amplifier amp,
Tuner tuner,
DvdPlayer dvd,
CdPlayer cd,
Projector projector,
Screen screen,
TheaterLights lights,
PopcornPopper popper) {
this.amp = amp;
this.tuner = tuner;
this.dvd = dvd;
this.cd = cd;
this.projector = projector;
this.screen = screen;
this.lights = lights;
this.popper = popper;
}
public void watchMovie(String movie) {
System.out.println("Get ready to watch a movie...");
popper.on();
popper.pop();
lights.dim(10);
screen.down();
projector.on();
projector.wideScreenMode();
amp.on();
amp.setDvd(dvd);
amp.setSurroundSound();
amp.setVolume(5);
dvd.on();
dvd.play(movie);
}
public void endMovie() {
System.out.println("Shutting movie theater down...");
popper.off();
lights.on();
screen.up();
projector.off();
amp.off();
dvd.stop();
dvd.eject();
dvd.off();
}
public void listenToCd(String cdTitle) {
System.out.println("Get ready for an audiopile experence...");
lights.on();
amp.on();
amp.setVolume(5);
amp.setCd(cd);
amp.setStereoSound();
cd.on();
cd.play(cdTitle);
}
public void endCd() {
System.out.println("Shutting down CD...");
amp.off();
amp.setCd(cd);
cd.eject();
cd.off();
}
public void listenToRadio(double frequency) {
System.out.println("Tuning in the airwaves...");
tuner.on();
tuner.setFrequency(frequency);
amp.on();
amp.setVolume(5);
amp.setTuner(tuner);
}
public void endRadio() {
System.out.println("Shutting down the tuner...");
tuner.off();
amp.off();
}
}
影院中各种视听设备类：
public class Amplifier {
String description;
Tuner tuner;
DvdPlayer dvd;
CdPlayer cd;
public Amplifier(String description) {
this.description = description;
}
public void on() {
System.out.println(description + " on");
}
public void off() {
System.out.println(description + " off");
}
public void setStereoSound() {
System.out.println(description + " stereo mode on");
}
public void setSurroundSound() {
System.out.println(description + " surround sound on (5 speakers, 1 subwoofer)");
}
public void setVolume(int level) {
System.out.println(description + " setting volume to " + level);
}
public void setTuner(Tuner tuner) {
System.out.println(description + " setting tuner to " + dvd);
this.tuner = tuner;
}
public void setDvd(DvdPlayer dvd) {
System.out.println(description + " setting DVD player to " + dvd);
this.dvd = dvd;
}
public void setCd(CdPlayer cd) {
System.out.println(description + " setting CD player to " + cd);
this.cd = cd;
}
public String toString() {
return description;
}
}
public class CdPlayer {
String description;
int currentTrack;
Amplifier amplifier;
String title;
public CdPlayer(String description, Amplifier amplifier) {
this.description = description;
this.amplifier = amplifier;
}
public void on() {
System.out.println(description + " on");
}
public void off() {
System.out.println(description + " off");
}
public void eject() {
title = null;
System.out.println(description + " eject");
}
public void play(String title) {
this.title = title;
currentTrack = 0;
System.out.println(description + " playing \"" + title + "\"");
}
public void play(int track) {
if (title == null) {
System.out.println(description + " can't play track " + currentTrack +
", no cd inserted");
} else {
currentTrack = track;
System.out.println(description + " playing track " + currentTrack);
}
}
public void stop() {
currentTrack = 0;
System.out.println(description + " stopped");
}
public void pause() {
System.out.println(description + " paused \"" + title + "\"");
}
public String toString() {
return description;
}
}
只列了部分代码，完整代码可到51下载中有。
测试类：
public class HomeTheaterTestDrive {
public static void main(String[] args) {
Amplifier amp = new Amplifier("Top-O-Line Amplifier");
Tuner tuner = new Tuner("Top-O-Line AM/FM Tuner", amp);
DvdPlayer dvd = new DvdPlayer("Top-O-Line DVD Player", amp);
CdPlayer cd = new CdPlayer("Top-O-Line CD Player", amp);
Projector projector = new Projector("Top-O-Line Projector", dvd);
TheaterLights lights = new TheaterLights("Theater Ceiling Lights");
Screen screen = new Screen("Theater Screen");
PopcornPopper popper = new PopcornPopper("Popcorn Popper");
HomeTheaterFacade homeTheater =
new HomeTheaterFacade(amp, tuner, dvd, cd,
projector, screen, lights, popper);
homeTheater.watchMovie("Raiders of the Lost Ark");//可看到只用户只需要知道一个方法就可以；
homeTheater.endMovie();
}
}