一个引用java接口但任何没有实现的源码解读_course

有个类一直无法理解，情况是这样的，该类有个内部接口，确定没有任何实现方法，怀疑代码不全需要自己补充，请高手支招确定下，第一次发帖，望大家捧捧场，谢谢！ PresenceEventDispatcher继承的一个引用自己内部接口的抽象类，有“<”刚被csdn隐藏了 public class PresenceEventDispatcher extends EventDispatcher\<PresenceEventDispatcher.PresenceEventListener\> { private final PresenceWorker presenceWorker = new PresenceWorker(); public void availableSession(ClientSession session) { if (!listeners.isEmpty()) { for (PresenceEventListener listener : listeners) { listener.availableSession(session); } } presenceChanged(session); } public void unavailableSession(ClientSession session) { if (!listeners.isEmpty()) { for (PresenceEventListener listener : listeners) { listener.unavailableSession(session); } } presenceChanged(session); } public void presenceChanged(ClientSession session) { if (!listeners.isEmpty()) { for (PresenceEventListener listener : listeners) { listener.presenceChanged(session, session.getPresence()); } } presenceWorker.push(session.getPresence()); } public interface PresenceEventListener extends EventListener { public void availableSession(ClientSession session); public void unavailableSession(ClientSession session); public void presenceChanged(ClientSession session, Presence presence); } } public abstract class EventDispatcher<T> { protected List<T> listeners = new CopyOnWriteArrayList<T>(); /** * Registers a listener to receive events. * * @param listener the listener. */ public void addListener(T listener) { if (listener == null) { throw new NullPointerException(); } listeners.add(listener); } /** * Unregisters a listener to receive events. * * @param listener the listener. */ public void removeListener(T listener) { listeners.remove(listener); } }