东阳企业网站微商城建设搜索引擎优化seo优惠

观察者模式：通过使用类之间的一对多的关系，当目标对象满足一定的条件的情况下，就可以通知观察者，让观察者做出相应的反应。

例子： （1）通用的观察者的模板（2） 测速器是目标对象，警车是观察者。

代码如下：

package observer;


public interface Observer {


public void update();
}

package ObserverInstance;


public class PoliceObserver implements Observer{


public void update() {
System.out.println("I am a police to catch the car that runs fast");
}
}

package ObserverInstance;


public abstract class Target {


private Observer observer;


public Observer getObserver() {
return observer;
}


public void setObserver(Observer observer) {
this.observer = observer;
}

public abstract void dowork();
public void notifyObserver(){
observer.update();
}
}

package ObserverInstance;


public class Speed extends Target 
{
private int speed;



public int getSpeed() {
return speed;
}




public void setSpeed(int speed) {
this.speed = speed;
}




public void dowork() {
if(speed<10){
System.out.println("the car can run");
}else{
this.notifyObserver();
}
}

}

package ObserverInstance;


public class Car {


private int speed;
private String color;
public int getSpeed() {
return speed;
}
public void setSpeed(int speed) {
this.speed = speed;
}
public String getColor() {
return color;
}
public void setColor(String color) {
this.color = color;
}
public Car(int speed, String color) {
this.speed = speed;
this.color = color;
}


}

package ObserverInstance;


public class Client {


public static void main(String[] args){
Car car=new Car(9,"red");
Observer observer=new PoliceObserver();
Speed speed=new Speed();
speed.setObserver(observer);
speed.setSpeed(car.getSpeed());
speed.dowork();
}
}