外观模式-Car(最少知识原则)

package H_Appearance;

/**
* 外观模式：提供一个统一的接口，用来访问子系统中的一群接口。外观定义了一个高层接口，让子系统更容易使用
* 简化接口时，依然将系统完整的功能暴露出来，供给需要的人用。将客户从组件的子系统中解耦
* 如果变得复杂，有太多的朋友牵涉其中，可以增加更多的外观，将子系统分成几个层次
* 设计原则：最少知识原则，只和你的密友谈话(减少对象之间交互，只留下几个”密友”)
* 要求：在该对象的方法内，只应该调用属于如下范围的方法
* 如果某对象是调用其他方法返回结果，不要调用该对象的方法
* 1：该对象本身
* 2：被当做方法的参数所传递的对象
* 3：此方法所创建或实例化的任何对象
* 4：对象的任何组件(被实例引用的任何对象，想象成has-a关系)
* 缺点：导致更多包装类被制造出来，已处理和其他组件的沟通
*
*
*/
public class Main {
public static void main(String[] args) {
Amplifier amp = new Amplifier();
Tuner tuner = new Tuner();
DvdPlayer dvd = new DvdPlayer();
CdPlayer cd = new CdPlayer();
Projector projector = new Projector();
TheaterLights lights = new TheaterLights();
Screen screen = new Screen();
PopcornPopper popper = new PopcornPopper();

    HomeTheaterFacade homeTheaterFacade = new HomeTheaterFacade(amp, tuner,            dvd, cd, projector, lights, screen, popper);    homeTheaterFacade.watchMovie("看电影");    homeTheaterFacade.endMovie();}

}
package H_Appearance;

import java.util.ArrayList;

/**
* 遵守最少知识原则，案例
*/
public class Car {
Engine engine;

public void start(Key key) {    Doors doors = new Doors();    boolean authorized = key.turns();// 被当做参数传递进来的对象，其方法可以被调用    if (authorized) {        engine.start();// 调用组件方法        updateDashboardDisplay();// 调用同一个对象内的本地方法        doors.lock();// 调用所创建或实例化的对象的方法    }    // 这样不行，没有遵守最小知识原则，因为在此调用的方法属于另一次调用的返回对象    // key.getObject().size();    // 但是可以再key里面添加一个显示size()结果的方法，这样可以减少所依赖的类的数目    int size = key.getSize();}private void updateDashboardDisplay() {}

}

class Engine {
public void start() {
}
}

class Doors {
public void lock() {
}
}

class Key {
public boolean turns() {
return false;
}

public ArrayList getObject() {    return new ArrayList();}public int getSize() {    return new ArrayList().size();}

}
package H_Appearance;

class Amplifier {

public void on() {    // TODO Auto-generated method stub}public void setDvd(DvdPlayer dvd) {    // TODO Auto-generated method stub}public void setSurroundSound() {    // TODO Auto-generated method stub}public void setVolume(int i) {    // TODO Auto-generated method stub}public void off() {    // TODO Auto-generated method stub}

}

class Tuner {

}

class DvdPlayer {

public void play(String movie) {    // TODO Auto-generated method stub}public void on() {    // TODO Auto-generated method stub}public void sto() {    // TODO Auto-generated method stub}public void eject() {    // TODO Auto-generated method stub}public void off() {    // TODO Auto-generated method stub}

}

class CdPlayer {

}

class Projector {

public void on() {    // TODO Auto-generated method stub}public void wideScreenMode() {    // TODO Auto-generated method stub}public void off() {    // TODO Auto-generated method stub}

}

class TheaterLights {

public void dim(int i) {    // TODO Auto-generated method stub}public void on(int i) {    // TODO Auto-generated method stub}

}

class Screen {

public void down() {    // TODO Auto-generated method stub}public void up() {    // TODO Auto-generated method stub}

}

class PopcornPopper {

public void on() {    // TODO Auto-generated method stub}public void pop() {    // TODO Auto-generated method stub}public void off() {    // TODO Auto-generated method stub}

}

public class HomeTheaterFacade {
// 组合
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, TheaterLights lights,        Screen screen, PopcornPopper popper) {    this.amp = amp;    this.tuner = tuner;    this.dvd = dvd;    this.cd = cd;    this.projector = projector;    this.lights = lights;    this.screen = screen;    this.popper = popper;}public void watchMovie(String 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() {    popper.off();    lights.on(10);    screen.up();    projector.off();    amp.off();    dvd.sto();    dvd.eject();    dvd.off();}

}