Getting error for generic interface: The interface Observer cannot be implemented more than once with different arguments:

Question

I am getting this error in Eclipse while writing a GWT app

The interface Observer cannot be implemented more than once with different arguments:

Answer 1

Because of type erasure you can't implement the same interface twice (with different type parameters). So, the eclipse error that you are receiving is correct.

You could add a base class for all possible "T", which may be limiting and not useful depending on the scope of these classes. And, you have requested a solution that prevents you from creating a multitude of Observer classes (i am assuming interfaces) for every possible event, well I can't see how else you would do that without compromising compile time safety.

I would suggest the following

interface Observer{
    public void update (T o);
}

interface DialogBoxAuthenticateObserver extends Observer{
}

The code clutter isn't horrible and if you place them all in one file, they will be easy to reference and maintain. Hope I have helped

EDIT: After some digging around on google (which pointed me back to stackoverflow!, your question was asked in a different fashion and answered similarly here