java simple and lightweight eventbus

EventBus.java

package wtf.cattyn.catbus;

import java.lang.annotation.ElementType;
import java.lang.annotation.Retention;
import java.lang.annotation.RetentionPolicy;
import java.lang.annotation.Target;
import java.lang.reflect.InvocationTargetException;
import java.lang.reflect.Method;
import java.util.*;
import java.util.concurrent.ConcurrentHashMap;
import java.util.concurrent.CopyOnWriteArrayList;
import java.util.stream.Collectors;

public final class EventBusImpl {
    private final Map<Object, List<Method>> listeners = new ConcurrentHashMap<>();

    public void post(Object event) {
        listeners.forEach((subscriber, methods) -> methods.stream().filter(method -> method.getParameterTypes()[0].equals(event.getClass())).forEach(method -> {
            try {
                method.invoke(subscriber, event);
            } catch (Throwable e) {
                e.printStackTrace();
            }
        }));
    }

    public void subscribe(Object o) {
        listeners.putIfAbsent(o, Arrays.stream(o.getClass().getDeclaredMethods())
                .filter(method -> method.isAnnotationPresent(Listener.class) && method.getParameterCount() == 1)
                .collect(Collectors.toCollection(CopyOnWriteArrayList::new)));
    }

    public void unsubscribe(Object o) {
        listeners.remove(o);
    }

    @Target(ElementType.METHOD)
    @Retention(RetentionPolicy.RUNTIME)
    public @interface Listener { }
}