观察者模式

package com.thread.ch4;

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

/**
 * 观察者模式
 */
public class Subject {
    //被观察的对象
    private List<Observer> observerList = new ArrayList<>();

    private int state;

    public int getState() {
        return state;
    }

    public void setState(int state) {
        if (state == this.state) {
            return;
        }
        this.state = state;
        notifyAllObserver();
    }

    public void attach(Observer observer) {
        observerList.add(observer);
    }

    public void notifyAllObserver() {
        observerList.stream().forEach(Observer::update);
    }
}


package com.thread.ch4;

public abstract class Observer {

    protected Subject subject;
    public Observer(Subject subject){
        this.subject = subject;
        this.subject.attach(this);
    }

    public abstract void update();

}

package com.thread.ch4;

public class BinaryObserver extends Observer {
    public BinaryObserver(Subject subject) {
        super(subject);
    }

    @Override
    public void update() {
        System.out.println(getClass()+",state="+ Integer.toBinaryString( subject.getState()));
    }
}


package com.thread.ch4;

public class OctalObserver extends Observer {

    public OctalObserver(Subject subject) {
        super(subject);
    }

    @Override
    public void update() {
        System.out.println(this.getClass()+",state="+Integer.toOctalString(subject.getState()));
    }
}


package com.thread.ch4;

public class ObserverClient {
    public static void main(String[] args) {
        final Subject subject = new Subject();
        new BinaryObserver(subject);
        new OctalObserver(subject);
        System.out.println("---------------------------");
        subject.setState(10);
        System.out.println("===========================");
        subject.setState(15);

    }
}

---------------------------
class com.thread.ch4.BinaryObserver,state=1010
class com.thread.ch4.OctalObserver,state=12
===========================
class com.thread.ch4.BinaryObserver,state=1111
class com.thread.ch4.OctalObserver,state=17

Process finished with exit code 0

 

来源：oschina

链接：https://my.oschina.net/lvzi98/blog/3165225