如题，我们先抽象出被观察者和观察者

/**
 *抽象观察者
 */
abstract class obServer {
    protected String name;
    public obServer(String name) {
        this.name = name;
    }
    protected SubJect subJect;
    //更新接口
    public abstract void updata();
    //不在观察
    public abstract void dontLook(SubJect subJect);
}

/**
 *抽象被观察者
 */
abstract class SubJect{
    //所有观察者
    private List<obServer> obServerList=new ArrayList<>();
    //状态
    private int state;
    public int getState() {
        return state;
    }
    public void setState(int state) {
        this.state = state;
    }
    //添加观察者
    public void attach(obServer obServer){
        obServerList.add(obServer);
        System.out.println("新增观察者："+obServer.name);
    }
    //删除观察者
    public void deletObServer(obServer obServer){
        obServerList.remove(obServer);
        System.out.println("移除观察者："+obServer.name);
    }
    //更新观察者
    public void updateObServer(){
        for (obServer o:obServerList) {
            o.updata();
        }
    }
}

有一档电视节目来当实体（被观察者）

class TVPlay extends SubJect{
    private String theTVSet;
    public String getTheTVSet() {
        return theTVSet;
    }
    public void setTheTVSet(String theTVSet) {
        this.theTVSet = theTVSet;
    }
    public void play(){
        System.out.println("电视剧开播了！今日节目："+ theTVSet);
        //通知观察者
        updateObServer();
    }
}

人实体来充当观察者

class People extends obServer{
    public People(String name) {
        super(name);
    }
    @Override
    public void updata() {
        System.out.println(name+"收到电视剧开播通知");
    }

    @Override
    public void dontLook(SubJect subJect) {
        subJect.deletObServer(this);
    }
}

执行时，被观察者会检查所有观察者，去调用play下发通知

 public static void main(String[] args) {
        TVPlay tvPlay = new TVPlay();
        People man = new People("男人");
        People woman = new People("女人");
        tvPlay.attach(man);
        tvPlay.attach(woman);
        tvPlay.setTheTVSet("宫锁心玉");
        tvPlay.play();

        System.out.println("新的一期开始了！");
        System.out.println("上次不好看，男人取消了观察");
        man.dontLook(tvPlay);
        tvPlay.setTheTVSet("宫锁心玉2");
        tvPlay.play();
    }