2019-12-17

一.设计图

二.代码

public class EventManager {
    private Map<Object, Set<Observe>> observableToObserve = new HashMap();//set集合可以去重
    private static EventManager instance;

    private EventManager() {
    }

    public static EventManager getInstance() {
        if (instance == null) {
            synchronized (EventManager.class) {
                if (instance == null) {
                    instance = new EventManager();
                }
            }
        }
        return instance;
    }

    /**
     * 完成观察者对被观察者的注册
     *
     * @param observable   事件
     * @param observe 事件的观察者
     */
    public void register(Object observable, Observe observe) {
        Set<Observe> observeSet = observableToObserve.get(observable);
        if (observeSet == null) {
            observeSet = new HashSet<>();
        }
        observeSet.add(observe);
        observableToObserve.put(observable,observeSet);
    }


    /**
     * 通知被观察者的观察者事件发生改变
     * @param observable
     */
    public void notify(Object observable) {
        Set<Observe> observes = observableToObserve.get(observable);
        if(observable!=null) {
            Iterator<Observe> iterator = observes.iterator();
            while (iterator.hasNext()) {
                Observe observe = iterator.next();
                observe.onObservableChange(observable);
            }
        }
    }

    /**
     * 取消观察者对被观察者的注册
     *
     * @param observable
     * @param observe
     */
    public void unRegister(Object observable, Object observe) {
        Set<Observe> observeList = observableToObserve.get(observable);
        if (observeList != null) {
            observeList.remove(observe);
        }
    }
}

public interface Observe {
    void onObservableChange(Object observable);
}

public class Test {
    public static void main(String[] args) {
        Worker worker1 = new Worker("work1");
        Worker worker2 = new Worker("work2");
        Worker worker3 = new Worker("work3");
        Boss boss = new Boss();
        boss.hireWork(worker1);
        boss.hireWork(worker2);
        boss.hireWork(worker3);
    }
}

class Worker {
    public String name;

    public Worker(String name) {
        this.name = name;
    }

    public void doingHomeWork() {
        try {
            Thread.sleep(3000);
        } catch (InterruptedException e) {
            e.printStackTrace();
        }
        System.out.println(name + " finished work");
        EventManager.getInstance().notify(this);
    }
}

class Boss implements Observe {

    public void hireWork(Worker worker) {
        EventManager.getInstance().register(worker, this);
        worker.doingHomeWork();
    }

    @Override
    public void onObservableChange(Object observable) {
        Worker worker = (Worker) observable;
        System.out.println("收到" + worker.name + "完成工作的通知");
    }
}