In the example you have detailed, RawBar is not a subtype of Bar<?> since it extends the raw type Bar.
-----Original Message----- From: Sebastiaan van Erk [mailto:[EMAIL PROTECTED] Sent: Friday, June 06, 2008 11:31 AM To: users@wicket.apache.org Subject: Re: (Class<? extends Page<?>>) casting troubles ARgh, you always make typos with this stuff. See correction. Sebastiaan van Erk wrote: > Martin Funk wrote: > >>> Class<? extends Page<?>> means "class of (anything that extends (page of >>> anything))". >> >> I'm not so sure. > > There are 2 separate issues: > > ISSUE 1: Foo<? extends Bar<?>> is not assignable from a Foo<RawBar> > where RawBar extends Bar as a raw type. That is, given: > > static class Foo<T> { > } > > static class Bar<T> { > } > > static class RawBar extends Bar { > } > > static class SubBar<T> extends Bar<T> { > } > > Thus: > > Bar<?> bar = new RawBar(); // works, because RawBar is a subtype of > Bar<?> > > But: > > Foo<? extends Bar<?>> rawbar = new RawBar(); // DOES NOT WORK - THIS > IS CAUSING ONE HALF OF ALL OUR HEADACHES (correction:) Foo<? extends Bar<?>> rawbar = new Foo<RawBar>(); // DOES NOT WORK - THIS IS CAUSING ONE HALF OF ALL OUR HEADACHES Btw, this does work (like you expect): Foo<? extends Bar<?>> rawbar2 = new Foo<SubBar<?>>(); > Note that this is the issue that complete baffles me, as RawBar is a > subtype of Bar<?>, so I *really* *really* *REALLY* have no idea why the > compiler chokes on this. > > ISSUE 2: The class literal of a generic type returns a class of a raw > type. Thus Foo.class return Class<Foo>. This is also really messed up, > because: > > Class<Foo> fc = Foo.class; > > compiles, but generates a warning (reference to raw type). But if you > type this in eclipse: > > x fc = Foo.class; > > and use eclipse quickfix to change "x" to the "correct" type, it'll > change it to precisely Class<Foo> (the JLS is very short about this, see > also > http://java.sun.com/docs/books/jls/third_edition/html/expressions.html#1 5.8.2). > > > So what the heck is the proper type for the class literal??? I couldn't > find any! > > Finally, note that when you define a method like this: > > static void method1(Foo<? extends Bar<?>> y) { > } > > it works like a charm for a new Foo<SubBar<String>>, i.e., the "Foo of > (anything that extends (bar of anything))" really is the correct > interpretation. > > It's just that the interaction with raw types is completely *foobar* > (pun intended). > > Regards, > Sebastiaan > > > > > > > ______________ The information contained in this message is proprietary and/or confidential. If you are not the intended recipient, please: (i) delete the message and all copies; (ii) do not disclose, distribute or use the message in any manner; and (iii) notify the sender immediately. In addition, please be aware that any message addressed to our domain is subject to archiving and review by persons other than the intended recipient. Thank you. _____________ --------------------------------------------------------------------- To unsubscribe, e-mail: [EMAIL PROTECTED] For additional commands, e-mail: [EMAIL PROTECTED]
