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Newsgroups: comp.lang.java.programmer
From: Andreas Leitgeb <avl@gamma.logic.tuwien.ac.at>
Subject: Re: eclipse and un-generics
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Date: 22 Oct 2011 23:04:42 GMT
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Joshua Cranmer <Pidgeot18@verizon.invalid> wrote:
> On 10/20/2011 12:11 PM, Andreas Leitgeb wrote:
>> My attempt to use  Class<?>  as argument type in the implementing
>> class failed, and I'm not sure I understand the deeper reasons of
>> why this has to fail. I.e. why it doesn't just see it as an override
>> instead of complaining about a bad overload.
> While Class<?> is often treated as being the generic equivalent of 
> Class, they're not quite the same thing. Logically, "Class" means "a 
> class of anything", while "Class<?>" means "a class of some unknown type".

I see the relevance for e.g. List<?> versus List where the former (unlike
the latter) could not be add()ed an Object-typed item.  I don't see, how it
could make a difference for Class<?> versus Class, of which no method takes
any "T"-typed arguments, nor do any methods of the "<T>"-parameterized
return-value-types (like e.g. Constructor<T>).
But then again, I do see, that the JLS just doesn't go that far into
analysis of where <?> does make a difference, and where it doesn't.

> Indeed, if anything, "Class" is probably closer in typing terms to 
> "Class<Object>", although there are a slew of special rules to account 
> for the fact that "Class<Object>" is probably very rarely meant.

I'll try on Monday (to be sure), but I really don't expect
(Class<Object> clazz) to be valid arguments for an overRIDE of
a superclass's method taking (Class clazz).

Anyway, I appreciate your response, making me aware that <?>
isn't semantically the closest to the bare type, afterall.