设计模式观察者模式(ObserverPatern)

/**
* Created by tory on 2018/1/3.
* 观察者模式
* 使用场景：一个对象发生改变时将自动通知其他对象
*/
public class ObserverPatern {
public static void main(String[] args) {
WeatherSubject weather = new WeatherSubject();
weather.register(new PhoneObserver());
weather.register(new ComputerObserver());
weather.publish("今天多云");
weather.publish("明天下雨");
}
}

//Subject 抽象主题，Obervable 被观察者/被订阅者
abstract class Subject {
protected String message;
private List<Observer> list;

public Subject() {
list = new ArrayList<>(8);
}

//订阅subscribe
public void register(Observer observer) {
list.add(observer);
}

//取消订阅
public void delete(Observer observer) {
list.remove(observer);
}

//发布内容
public void publish(String message) {
this.message = message;
for (Observer observer : list) {
observer.update(this, message);
}
}
}

//Observer 抽象观察者，
interface Observer {
public void update(Subject all, String message);
}

//ConcreteSubject具体被观察者,被订阅的主题
class WeatherSubject extends Subject {
String city;
String wind;
String quality;
String humidity;

WeatherSubject() {
city = "成都";
wind = "3级";
quality = "200";
humidity = "相对湿度80%";
}
}

//ContreObserver 具体订阅者
class PhoneObserver implements Observer {
//手机订阅天气
@Override
public void update(Subject all, String message) {
System.out.println("手机收到消息：" + message);
}
}

//ContreObserver 具体订阅者
class ComputerObserver implements Observer {
//电脑订阅天气
@Override
public void update(Subject all, String message) {
if (all instanceof WeatherSubject) {
WeatherSubject weather = (WeatherSubject) all;
System.out
.println("电脑收到消息：" + weather.message + " " + weather.city + " " + weather.quality + " " + weather
.humidity);
} else {
System.out.println("电脑收到消息：" + message);
}
}
}