设计模式学习笔记——观察者模式

观察者模式类图(截图来自《大话设计模式》ps:以生活中的故事来分析设计模式，使人不觉得枯燥无味，很赞的一本书！)：

代码结构图：

Java版代码：

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("老板回来了");
        subject.inform();
    }

}

abstract class Subject {
    private String sbjectState;
    private ArrayList<AbstractObserver> 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()
                + "关闭股票行情，继续工作！");
    }
}

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()
                + "关闭NBA直播，继续工作！");
    }
}