弱事件模式对源和监听器都弱吗？

弱事件模式是一种设计模式，它在事件传递的过程中使用弱引用，以避免因为强引用导致的内存泄漏。因此，它是对于源和监听器都弱的。

以下是使用弱事件模式的示例。假设我们有一个“Person”类，每个“Person”实例都可以注册在一个“EventManager”上。我们使用弱事件模式来监听“Person”的变化：

public class Person {
    private String name;
    private int age;
    private EventManager eventManager;

    public Person(String name, int age, EventManager eventManager) {
        this.name = name;
        this.age = age;
        this.eventManager = eventManager;
    }

    public void setName(String name) {
        this.name = name;
        this.eventManager.notifyListeners(new PropertyChangeEvent(this, "name", null, name));
    }

    public void setAge(int age) {
        this.age = age;
        this.eventManager.notifyListeners(new PropertyChangeEvent(this, "age", null, age));
    }
}

public class EventManager {
    private Map<String, List<WeakReference<EventListener>>> listeners = new HashMap<>();

    public void addListener(String eventName, EventListener listener) {
        List<WeakReference<EventListener>> eventListeners = listeners.computeIfAbsent(eventName, k -> new ArrayList<>());
        eventListeners.add(new WeakReference<>(listener));
    }

    public void notifyListeners(PropertyChangeEvent event) {
        List<WeakReference<EventListener>> eventListeners = listeners.get(event.getPropertyName());
        if (eventListeners != null) {
            for (Iterator<WeakReference<EventListener>> it = eventListeners.iterator(); it.hasNext(); ) {
                WeakReference<EventListener> reference = it.next();
                EventListener listener = reference.get();
                if (listener == null) {
                    it.remove(); // remove the dead listener
                } else {
                    listener.propertyChanged(event); // notify the listener
                }
            }
        }
    }
}

public interface EventListener {
    void propertyChanged(PropertyChangeEvent event);
}

public class MyEventListener implements EventListener {
    @Override
    public void propertyChanged(Property