一个引用java接口但任何没有实现的源码解读

Question

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 {

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);
}

}

Answer 1

语法上就报错了吧，public interface PresenceEventListener 方法？