import java.util.ArrayList;

/**
 * @Auther: Arsenal
 * @Date: 2020-03-20 22:46
 * @Description: 观察者模式
 */
public class ObserverDemo {
    public static void main(String[] args) {
        Subject subject = new ConcreteSubject();
        Observer observer = new ConcreteObserver("观察者一号");
        Observer observer2 = new ConcreteOberverOther("观察者二号");
        subject.attach(observer);
        subject.attach(observer2);
        subject.notifyObserver();

    }
}

/**
 * 目标抽象类 Subject
 */
abstract class Subject {

    protected ArrayList observers = new ArrayList<>();

    //把观察者对象添加到观察者集合中
    public void attach(Observer observer) {
        observers.add(observer);
    }

    //把观察者对象剔除到观察者集合中
    public void detach(Observer observer) {
        observers.remove(observer);
    }

    //声明抽象方法
    public abstract void notifyObserver();
}

/**
 * 具体目标类 ConcreteSubject
 */
class ConcreteSubject extends Subject {

    //实现通知的方法
    @Override
    public void notifyObserver() {
        System.out.println("目标对象状态已变化......发送通知给观察者中");
        for (Object object : observers) {
            ((Observer) object).update();
        }
    }
}

/**
 * 观察者接口 Observer
 */
interface Observer {
    public void update();
}

/**
 * 具体的观察者
 */
class ConcreteObserver implements Observer {
    private String observerName;

    public ConcreteObserver(String observerName) {
        this.observerName = observerName;
    }

    @Override
    public void update() {
        System.out.println(observerName + "我要更新一下我的状态了......");
    }
}

/**
 * 具体的观察者
 */
class ConcreteOberverOther implements Observer {

    private String observerName;

    public ConcreteOberverOther(String observerName) {
        this.observerName = observerName;
    }

    @Override
    public void update() {
        System.out.println(observerName + "我要更新一下我的状态了......");
    }
}