Getting the class of a type parameter

[dlorde]

My problem is that I don't have an object of T in my class and I'm not planning on getting one. I have an ArrayList<T> though - but I'm not aware of any way to get it's parametrized type - and the list is allowed to be empty, so I can't just get an object inside it.

Ah, OK. Norm is right, generics is a compile-time thing, erasure removes it from the runtime (mostly), so you need an object to work with.

There is a way to retain generic types for classes, which relys on the need for anonymous classes to retain their generic type information at runtime.

I only browsed through the earlier part of the thread, so this may already have been mentioned - ignore the following if so...

Using this technique, you could subclass a collection class such as ArrayList, to make the generic type available at runtime. See Using Type Tokens To Retrieve Generic Parameters and Super Type Tokens.

It's a bit of a hack though...

[Muskar]

Ah, OK. Norm is right, generics is a compile-time thing, erasure removes it from the runtime (mostly), so you need an object to work with.

There is a way to retain generic types for classes, which relys on the need for anonymous classes to retain their generic type information at runtime.

I only browsed through the earlier part of the thread, so this may already have been mentioned - ignore the following if so...

Using this technique, you could subclass a collection class such as ArrayList, to make the generic type available at runtime. See Using Type Tokens To Retrieve Generic Parameters and Super Type Tokens.

It's a bit of a hack though...

Thanks it made me understand what the problem with type erasure is. It makes me a bit sad though, since my work will not be as awesome, and easy to implement for users, as intended but I think I'll create constructors to open up for both solutions:

• Taking the class as a parameter in the constructor
• Or requiring instantiation of my class to be anonymous

So people can do what they find easiest - although I would've liked to be able to have one with an empty constructor since it would be easier for newbs.

Anyway, I'll edit this post with the code if my solution will work. Otherwise I'll probably do another post about my problems.