public class Akkatutorial {   /**   * @param args the command line arguments   */   public static void main(String[] args) {   ActorSystem system=ActorSystem.create("Hola");   ActorRef helloActor = system.actorOf(new Props(HelloActor.class), "hola");   helloActor.tell("hello",null);   helloActor2.tell("hello",null);   system.shutdown();   system.awaitTermination();//JOIN   }  }  class HelloActor extends UntypedActor{   @Override   public void onReceive(Object message) throws Exception {   if(message instanceof String ) {   String s=(String)message;   switch (s){   case "hello":{   System.out.println("hello you");   break;   }   default:   System.out.println("huu?");   }   }   else{   unhandled(message);   }   }