Avoiding 'instanceof' in Java

Question

I have the following (maybe common) problem and it absolutely puzzles me at the moment:

There are a couple of generated event objects which extends the abstract clas

Answer 1

The simplest approach is to have the Event provide a method you can call so the Event knows what to do.

interface Event {
    public void onEvent(Context context);
}

class DocumentEvent implements Event {
    public void onEvent(Context context) {
         context.getDocumentGenerator().gerenateDocument(this);
    }
}

class MailEvent implements Event {
    public void onEvent(Context context) {
         context.getDeliveryManager().deliverMail(event);
    }
}


class Context {
    public void divideEvent(Event event) {
        event.onEvent(this);
    }
}