java - How do I make an annotation based event system? -

well made 1 don't know if it's best tbh. can write me tutorial? made 1 tutorial , understood 90% of 10% of off , seems aint best way it.

eventmanager.java

public class eventmanager {

private static list<listener> registered = new arraylist<listener>();  public static void register(listener listener) {     if (!registered.contains(listener)) {         registered.add(listener);     } }  public static void unregister(listener listener) {     if (registered.contains(listener)) {         registered.remove(listener);     } }  public static list<listener> getregistered() {     return registered; }  public static void callevent(final event event) {     new thread() {         @override         public void run() {             call(event);         }     }.start(); }  private static void call(final event event) {     (listener registered : getregistered()) {         method[] methods = registered.getclass().getmethods();          (int = 0; < methods.length; i++) {             eventhandler eventhandler = methods[i].getannotation(eventhandler.class);             if (eventhandler != null) {                 class<?>[] methodparams = methods[i].getparametertypes();                  if (methodparams.length < 1) {                     continue;                 }                  if (!event.getclass().getsimplename().equals(methodparams[0].getsimplename())) {                     continue;                 }                  try {                     methods[i].invoke(registered.getclass().newinstance(), event);                 } catch (exception exception) {                     system.err.println(exception);                 }             }         }      } } 

}

eventhandler.java

@retention(retentionpolicy.runtime) @target(elementtype.method) public @interface eventhandler {  } 

and event.java , listener.java blank interfaces.