觀察者模式類圖(截圖來(lái)自《大話設(shè)計(jì)模式》ps:以生活中的故事來(lái)分析設(shè)計(jì)模式，使人不覺(jué)得枯燥無(wú)味，很贊的一本書(shū)！)：

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代碼結(jié)構(gòu)圖：

Java版代碼：

import java.util.ArrayList;

public class Observer {
public static void main(String[] args) {
        Subject subject= new Secretary();
        AbstractObserver observer1= new StockObserver("Marry", subject);
        AbstractObserver observer2= new NBAObserver("Peter", subject);

        subject.attach(observer1);
        subject.attach(observer2);

        subject.setSbjectState("老板回來(lái)了");
        subject.inform();
    }

}

abstract class Subject {
private String sbjectState;
private ArrayList observers = new ArrayList<>();

public void attach(AbstractObserver observer) {
        observers.add(observer);
    }

public void detach(AbstractObserver observer) {
        observers.remove(observer);
    }

public String getSbjectState() {
return sbjectState;
    }

public void setSbjectState(String sbjectState) {
this.sbjectState = sbjectState;
    }

public void inform() {
for (AbstractObserver o : observers) {
            o.update();
        }
    }
}

class Boss extends Subject {
}

class Secretary extends Subject {
}

abstract class AbstractObserver {
private String name;
private Subject sub;

public AbstractObserver(String name, Subject sub) {
this.setName(name);
this.setSub(sub);
    }

public abstract void update();

public String getName() {
return name;
    }

public void setName(String name) {
this.name = name;
    }

public Subject getSub() {
return sub;
    }

public void setSub(Subject sub) {
this.sub = sub;
    }
}

class StockObserver extends AbstractObserver {
public StockObserver(String name, Subject sub) {
super(name, sub);
    }

public void update() {
        System.out.println(this.getSub().getSbjectState() + this.getName()
+ "關(guān)閉股票行情，繼續(xù)工作！");
    }
}

class NBAObserver extends AbstractObserver {
public NBAObserver(String name, Subject sub) {
super(name, sub);
    }

    @Override
public void update() {
        System.out.println(this.getSub().getSbjectState() + this.getName()
+ "關(guān)閉NBA直播，繼續(xù)工作！");
    }
}

分享名稱：設(shè)計(jì)模式學(xué)習(xí)筆記——觀察者模式-創(chuàng)新互聯(lián)
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