单线程观察者模式

/**
 * @ClassName:Subject
 * @Author:linianest
 * @CreateTime:2020/3/23 9:38
 * @version:1.0
 * @Description TODO: 观察者观察的主题
 */
public class Subject {
    List<Observer> observers = new ArrayList<>();

    private int state;

    public int getState() {
        return state;
    }

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

        this.state = state;
        notifyAllobserver();
    }

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

    private void notifyAllobserver() {
        observers.stream().forEach(Observer::update);
    }
}

观察者

/**
 * 定义观察者内容与方法
 */
public abstract class Observer {

    protected Subject subject;

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

    abstract void update();
}

2进制

/**
 *@ClassName:BinaryObserver
 *@Author:linianest
 *@CreateTime:2020/3/23 10:27
 *@version:1.0
 *@Description TODO: 二进制观察者
 */
public class BinaryObserver extends Observer{
    public BinaryObserver(Subject subject){
        super(subject);
    }
    @Override
    public void update() {
        System.out.println("Binary String:"+Integer.toBinaryString(subject.getState()));
    }
}

8进制

/**
 * @ClassName:BinaryObserver
 * @Author:linianest
 * @CreateTime:2020/3/23 10:27
 * @version:1.0
 * @Description TODO: 八进制观察者
 */
public class OctalObserver extends Observer {
    public OctalObserver(Subject subject) {
        super(subject);
    }


    @Override
    public void update() {

        System.out.println("Octal String:" + Integer.toOctalString(subject.getState()));
    }
}

观察者客户端

/**
 * @ClassName:psvm
 * @Author:linianest
 * @CreateTime:2020/3/23 11:29
 * @version:1.0
 * @Description TODO: 观察者模式客户端
 */
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(10);
        System.out.println("======================");
        subject.setState(15);
    }

}