用Java写一段多线程实现观察者模式的代码

可以的，以下是Java多线程实现观察者模式的代码：

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

public class ObserverPattern {

    public static void main(String[] args) {
        Subject subject = new Subject();
        new ObserverA(subject);
        new ObserverB(subject);
        subject.setState(1);
        subject.setState(2);
    }
}

interface Observer {
    void update(int state);
}

class ObserverA implements Observer {
    public ObserverA(Subject subject) {
        subject.addObserver(this);
    }

    @Override
    public void update(int state) {
        System.out.println("ObserverA received state: " + state);
    }
}

class ObserverB implements Observer {
    public ObserverB(Subject subject) {
        subject.addObserver(this);
    }

    @Override
    public void update(int state) {
        System.out.println("ObserverB received state: " + state);
    }
}

class Subject {
    private List<Observer> observers = new ArrayList<>();
    private int state;

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

    public void removeObserver(Observer observer) {
        observers.remove(observer);
    }

    public void setState(int state) {
        this.state = state;
        notifyObservers();
    }

    private void notifyObservers() {
        for (Observer observer : observers) {
            observer.update(state);
        }
    }
}