观察者模式(发布-订阅 Publish/Subscribe)

参考

• https://blog.csdn.net/minyunfei6/article/details/140534620

import lombok.Getter;
import lombok.Setter;

import java.util.ArrayList;
import java.util.List;



abstract class Subject{
    private List<Observer> observers =new ArrayList<>();

    public void attach(Observer observer){
        observers.add(observer);
    }
    public void detach(Observer observer){
        observers.remove(observer);
    }

    public void notice(){
        observers.forEach(it->it.update());
    }

}
abstract class Observer{

    public abstract void update();
}
class ConcreteSubject extends Subject{
    @Getter
    @Setter
    private String name;


}
class ConcreteObserver1 extends Observer{
    private ConcreteSubject subject;
    public ConcreteObserver1(ConcreteSubject subject){
        this.subject = subject;
    }
    @Override
    public void update() {
        System.out.println("观察者ConcreteObserver1观察到，通知者"+subject.getName()+"的通知！");
    }
}
class ConcreteObserver2 extends Observer{
    private ConcreteSubject subject;
    public ConcreteObserver2(ConcreteSubject subject){
        this.subject = subject;
    }
    @Override
    public void update() {
        System.out.println("观察者ConcreteObserver2观察到，通知者"+subject.getName()+"的通知！");
    }
}
public class test {

    public static void main(String[] args) {
        ConcreteSubject concreteSubject =new ConcreteSubject();
        concreteSubject.setName("zs");
        concreteSubject.attach(new ConcreteObserver1(concreteSubject));
        concreteSubject.attach(new ConcreteObserver2(concreteSubject));
        concreteSubject.notice();
    }

}