MVC w/ event handlers and observers

ControllerTest.java

import java.util.*;

public class ControllerTest {
    
    private static Controller controller = Controller.getInstance();
    private static View view = new View();
    private static LoginHandler loginHandler = new LoginHandler();
    
    public static void main(String[] args) {
        
        controller.registerEventHandler(LoginEvent.class, loginHandler);
        controller.registerForEventNotification(LoginEvent.class, view);
        controller.handleEvent(new LoginEvent());
    }
    
}

//Your controller
class Controller {
    
    private static Controller INSTANCE = new Controller();
    private Map<Class, EventHandler> handlers = new HashMap<Class, EventHandler>();
    private Map<Class, ArrayList<Observer>> obs = new HashMap<Class, ArrayList<Observer>>();
    private BusinessManager mngr = new BusinessManager();
    
    private Controller(){
    }
    
    public static Controller getInstance() {
        return INSTANCE;
    }
    
    public BusinessManager getBusinessManager() {
        return mngr;
    }
       
    public void handleEvent(Event evt) {
        handlers.get(evt.getClass()).handle(evt, obs.get(evt.getClass()));
    }
    
    public void registerEventHandler(Class evtClass, EventHandler handler) {
        handlers.put(evtClass, handler);
    }
    
    public void registerForEventNotification(Class evtClass, Observer o) {
        ArrayList<Observer> evtObs = obs.get(evtClass);
        if(evtObs == null) {
            evtObs = new ArrayList<Observer>();
            obs.put(evtClass, evtObs);
        }
        evtObs.add(o);
    }
}

class LoginHandler implements EventHandler {
    
    public LoginHandler() {
    }
    
    public void handle(Event evt, List<Observer> obs) {
        Response resp = Controller.getInstance().getBusinessManager().handle(evt);
        if(resp.getResult() == Response.SUCCESS) {
            for(Observer o: obs)
                o.observe();
        }
    }
}

//Your view
class View implements Observer {
    
    public View() {
    }
    
    public void observe() {
        System.out.println("Notified of login, loading data.");
    }
}

//Your model
class BusinessManager {
    
    public BusinessManager() {
    }
    
    public Response handle(Event evt) {
        if(evt instanceof LoginEvent) 
            return login();
        return null;
    }
    
    public Response login() {
        return new LoginResponse(Response.SUCCESS);
    }
}

class LoginResponse implements Response {
    
    private int result;
    
    public LoginResponse(int result) {
        this.result = result;
    }
    
    public int getResult() {
        return result;
    }
}

class Event{}
class LoginEvent extends Event{}
interface EventHandler { void handle(Event evt, List<Observer> obs); }
interface Observer { void observe(); }
interface Response { int SUCCESS = 1, FAIL = 0; int getResult(); }