Question

I have a class ClassA with some methods returning items:

class ClassA {
    ClassA item(...) {...}
    Vector<ClassA> list(...) {...}
}

These methods process an input and generate on the fly these kind of items. Now imagine I extend this class:

class ClassB extends ClassA {
    ...
}

I do not override item() or list() methods in any case, but I’d like them to return a ClassB item (or vector of) without casting on the return (which is my current solution now). Is there any way to do so? Thanks in advance.

Answer 1

I would create a third class (ClassC) to hold your ClassA or ClassB items, that is parametrized with a generic type like this:

class ClassC<T extends ClassA> {
    T item(...) {...}
    Vector<T> list(...) {...}
}

Now you can instantiate ClassC with either a ClassA or ClassB type and never have to worry about class casting.