Java事件系统通用转换为有界通配符

我正在制作我自己的事件系统，并试图使它像这样可用.

EventSystem.get(EventClientStart.class)
    .setCallback((event) -> {
        System.out.println("Client Started");
    });

EventSystem.get(EventClientStart.class)
    .invoke(new EventClientStart());

但我对类型的判断有问题，我错过了什么？ T扩展了Event，我认为它应该工作，它实际上是(只有当我将它转换为(EventController)，但然后我会得到警告"未判断的转换")

EventSystem.java

package im.silkproject.event;

import im.silkproject.event.internal.EventController;

import java.util.HashMap;
import java.util.Map;

public final class EventSystem
{
    private static final Map<Class<? extends Event>, EventController<? extends Event>> map = new HashMap<>();

    private EventSystem() { }

    public static <T extends Event> EventController<T> get(Class<T> event)
    {
        return map.computeIfAbsent(event, k -> new EventController<>());
    }
}

♪Event.Java♪

package im.silkproject.event;

public class Event
{
    private boolean cancelled;

    public void cancel()
    {
        cancelled = true;
    }

    public boolean isCancelled()
    {
        return cancelled;
    }
}

EventCallback.java

package im.silkproject.event.internal;

@FunctionalInterface
public interface EventCallback<T>
{
    void __call(T event);
}

EventController.java

package im.silkproject.event.internal;

import java.util.concurrent.CopyOnWriteArrayList;

public class EventController<T>
{
    private final CopyOnWriteArrayList<EventCallback<T>> callbacks = new CopyOnWriteArrayList<>();

    public void invoke(T event)
    {
        for (EventCallback<T> callback : callbacks)
        {
            callback.__call(event);
        }
    }

    public int length()
    {
        return callbacks.size();
    }

    public boolean setCallback(EventCallback<T> event)
    {
        return callbacks.addIfAbsent(event);
    }

    public boolean unsetCallback(EventCallback<T> event)
    {
        return callbacks.remove(event);
    }
}