『蚂蚁学模式』之实例化门面（Facade）模式

门面模式是对象的结构模式。
门面模式要求 一个子系统的外部与其内部的通信必须通过一个统一的门面（Facade）对象进行。

何时使用？
1. 为一个复杂子系统提供一个简单接口
2. 子系统的独立性
3. 层次化结构

对象图示意：


1. com.cleversoft.designpatterns.facade.Alarm.java:

package  com.cleversoft.designpatterns.facade;

public   class  Alarm {
     public   void  activate() {
        System.out.println( " Activating the alarm. " );
    }

     public   void  deactivate() {
        System.out.println( " Deactivating the alarm. " );
    }

     public   void  ring() {
        System.out.println( " Ring the alarm. " );
    }

     public   void  stopRing() {
        System.out.println( " Stop the alarm. " );
    }
}

2. com.cleversoft.designpatterns.facade.Camera.java:

package  com.cleversoft.designpatterns.facade;

public   class  Camera {
     public   void  turnOn() {
        System.out.println( " Turning on the camera. " );
    }

     public   void  turnOff() {
        System.out.println( " Turning off the camera. " );
    }

     public   void  rotate( int  degrees) {
        System.out.println( " Rotating the camera by  "   +  degrees  +   "  degrees. " );
    }
}

3. com.cleversoft.designpatterns.facade.Light.java:

package  com.cleversoft.designpatterns.facade;

public   class  Light {
     public   void  turnOn() {
        System.out.println( " Turning on the light. " );
    }

     public   void  turnOff() {
        System.out.println( " Turning off the light. " );
    }

     public   void  changeBulb() {
        System.out.println( " Changing the light-bulb. " );
    }
}

4. com.cleversoft.designpatterns.facade.Sensor.java:

package  com.cleversoft.designpatterns.facade;

public   class  Sensor {
     public   void  activate() {
        System.out.println( " Activating on the sensor. " );
    }

     public   void  deactivate() {
        System.out.println( " Deactivating on the sensor. " );
    }

     public   void  trigger() {
        System.out.println( " The sensor has been triggered. " );
    }
}

5. com.cleversoft.designpatterns.facade.SecurityFacade.java:

package  com.cleversoft.designpatterns.facade;

public   class  SecurityFacade {
     private  Camera camera1, camera2;

     private  Light light1, light2, light3;

     private  Sensor sensor;

     private  Alarm alarm;

     public  SecurityFacade() {
        camera1  =   new  Camera();
        camera2  =   new  Camera();
        light1  =   new  Light();
        light2  =   new  Light();
        light3  =   new  Light();
        sensor  =   new  Sensor();
        alarm  =   new  Alarm();
    }

     public   void  activate() {
        camera1.turnOn();
        camera2.turnOn();

        light1.turnOn();
        light2.turnOn();
        light3.turnOn();

        sensor.activate();
        alarm.activate();
    }

     public   void  deactivate() {
        camera1.turnOff();
        camera2.turnOff();

        light1.turnOff();
        light2.turnOff();
        light3.turnOff();

        sensor.deactivate();
        alarm.deactivate();
    }
}

6. com.cleversoft.designpatterns.facade.Client.java:

package  com.cleversoft.designpatterns.facade;

public   class  Client {
     private   static  SecurityFacade security  =   new  SecurityFacade();

     public   static   void  main(String[] args) {
        security.activate();
    }
}

参考资料：
1. 《Java与模式》

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