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文章目录
  1. 观察者模式

观察者模式

  • 定义对象间的一种一对多的依赖关系，当一个对象的状态发生改变时，所有依赖于它的对象都得到通知并被自动更新。
    Observer
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public class Subject {
    private List<Observer> observers;
    public Subject() {
        observers = new ArrayList<>();
    }
    protected void attach(Observer observer) {
        observers.add(observer);
    }
    protected void detach(Observer observer) {
        observers.remove(observer);
    }
    protected void notify_(Object args) {
        observers.forEach(observer -> observer.update(args));
    }
}
public class VolumeSubject extends Subject {
    private Integer vol;
    public void changeVol(Integer vol){
        this.vol=vol;
        notify_(vol);
    }
}
public interface Observer {
    void update(Object message);
}
public class SpeakerObserver implements Observer {
    public SpeakerObserver(Subject subject){
        subject.attach(this);
    }
    @Override
    public void update(Object vol) {
        System.out.println("扬声器音量调整"+vol);
    }
}
public class VolumeBarObserver implements Observer {
    public VolumeBarObserver(Subject subject){
        subject.attach(this);
    }
    @Override
    public void update(Object vol) {
        System.out.println("音量条显示器调整"+vol);
    }
}
public class App {
    public static void main(String[] args) {
        VolumeSubject subject=new VolumeSubject();
        Observer speaker=new SpeakerObserver(subject);
        Observer volumeBar=new VolumeBarObserver(subject);
        subject.changeVol(4);
        subject.changeVol(5);
        subject.changeVol(6);
    }
}
文章目录
  1. 观察者模式