Generics and type erasure

11-05-06, 09:56 PM

Martin Lorentzson

I would like to determine the class value of a generic type. Is it
possible?

Right now, I'm passing the type as a parameter to the class
constructor:

public class Example<T extends Enum<T>> {

private final Class<T> clazz;

protected Example(Class<T> clazz) {
this.clazz = clazz;
}

public T parse(String text) {
// Can I derive the value of clazz from T?
T value = T.valueOf(clazz, text);
return value;
}
}

But I'm wondering if I can derive the class value of T instead of
using a constructor parameter or is type erasure as play here?

/Martin

11-05-06, 10:17 PM

Daniel Pitts

Martin Lorentzson wrote:
[..]
> // Can I derive the value of clazz from T?
> T value = T.valueOf(clazz, text);
> return value;
> }
> }
>
> But I'm wondering if I can derive the class value of T instead of
> using a constructor parameter or is type erasure as play here?
>
> /Martin

In fact, you cannot. That is the whole point(problem) of erasure.
Even the EnumMap and EnumSet classes require a Class object in their
construction.

11-06-06, 09:02 PM

Martin Lorentzson

"Daniel Pitts" <googlegroupie> writes:

> In fact, you cannot. That is the whole point(problem) of erasure.

OK, I thought I figured as much from the docs but I just wanted to
make sure. Thanks.

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