this is the usecase we are talking about. i get a compile error, which sucks.
public class Test
{
public static void main(String[] args)
{
Foo foo = new FooImpl();
foo.foo(IntegerComponent.class); // ok
foo.foo(Component.class); // compile error
}
public static class Component<T> {}
public static class IntegerComponent extends Component<Integer> {}
public static interface Foo
{
public void foo(Class< ? extends Component< ? >> clazz);
}
public static class FooImpl implements Foo
{
public void foo(Class< ? extends Component< ? >> clazz) {}
}
}
-igor
On Wed, May 14, 2008 at 11:56 PM, Sebastiaan van Erk
<[EMAIL PROTECTED]> wrote:
> Igor Vaynberg wrote:
>>
>> well, apparently johan ran into a situation where component<?> is too
>> restrictive...
>
> As I understand it, Johan ran into a situation where Component<?> causes
> *warnings* for users who use raw types. Which I've been arguing all along
> that they SHOULD get: they should use Component<Object> or Component<Void>
> instead of raw types, or live-with/suppress the warning.
>
> To make it clear, I made the following test class:
>
> public class Test<T> {
>
> public void doTest(Test<? extends Test<?>> test) {
> System.out.println("test");
> }
>
> public static void main(String[] args) {
> Test<Test<Integer>> test1 = newInstance(); // fine - no
> warnings.
> Test<Test> test2 = newInstance(); // not fine, use of raw
> type, warning
> Test test3 = newInstance(); // not fine, use of raw type,
> warning
>
> test1.doTest(test1); // fine - no warnings.
> test1.doTest(test2); // error - generic types don't match,
> can be "fixed" by line below
> test1.doTest((Test) test2); // warning - unchecked conversion
> test1.doTest(test3); // warning - unchecked conversion
> }
>
> public static <T> Test<T> newInstance() {
> return new Test<T>();
> }
> }
>
> As you can see, there is only one case when you get a compile error when
> using the <? extends Test<?>> generic type, and that is a case where there
> is on the user side an incorrect generic type: Test<Test>. The user here
> declares he's using generics, but then inserts a raw type of a known generic
> type - a situation that should not happen.
>
> Regards,
> Sebastiaan
>
>> -igor
>>
>>
>> On Wed, May 14, 2008 at 2:37 PM, Sebastiaan van Erk <[EMAIL PROTECTED]>
>> wrote:
>>>
>>> Igor Vaynberg wrote:
>>>>
>>>> since then the thread has evolved into whether or not we should use <?
>>>> extends Component> or <? extends Component<?>>
>>>>
>>>> -igor
>>>
>>> I don't understand how that changes any of my points. The first is
>>> incorrect
>>> (from a generics point of view) since you're referencing an
>>> unparameterized
>>> generic type.
>>>
>>> So the second gives warnings only in code that is not properly
>>> generified...
>>>
>>> Regards,
>>> Sebastiaan
>>>
>>>
>>>> On Wed, May 14, 2008 at 1:54 PM, Sebastiaan van Erk
>>>> <[EMAIL PROTECTED]>
>>>> wrote:
>>>>>
>>>>> Igor Vaynberg wrote:
>>>>>
>>>>>> i do like generics. did i ever say otherwise? the problem here is that
>>>>>> if we scope something as Class<? extends Component> then even though
>>>>>> you ARE using generics in your code you will still get a warning
>>>>>> because we did not scope the class as Class<? extends Component<?>>.
>>>>>>
>>>>>> on the other hand if we do scope it as Class<? extends Component<?>>
>>>>>> then you can no longer pass a raw reference when calling the function.
>>>>>
>>>>> But that's exactly the point isn't it? If you're using generics then
>>>>> you
>>>>> shouldn't be using raw Components anymore...
>>>>>
>>>>>> so we are screwed if we do and we are screwed if we dont, i expected
>>>>>> generics to be better.
>>>>>
>>>>> Well they definitely could have been better (erasure is terrible if you
>>>>> ask
>>>>> me), but I don't see what's wrong in this case. It warns you if you
>>>>> should
>>>>> be using a parameterized type but you don't.
>>>>>
>>>>>>> And especially if you look at the vote result, I think the majority
>>>>>>> wants
>>>>>>> the generics...
>>>>>>
>>>>>> that vote was before we uncovered this issue. we voted on the idea of
>>>>>> generics, not on the implementation.
>>>>>
>>>>> That's true, but I wonder if this issue would change the vote much. I
>>>>> don't
>>>>> really understand why it's an issue, because you can use generified
>>>>> Components always: Component<Object> if you don't want to constrain the
>>>>> model object, and Component<Void> if you don't need a model.
>>>>>
>>>>> The question that started the thread was about StringResourceModel
>>>>> which
>>>>> was
>>>>> not yet generified, and in that case, the warning seems to me to be
>>>>> perfectly ok: it just says StringResourceModel should be generified.
>>>>> It's
>>>>> not a release yet, so that some users who use the current snapshot run
>>>>> into
>>>>> these kind of warnings which cannot be removed seems to be fine to
>>>>> me...
>>>>>
>>>>> Regards,
>>>>> Sebastiaan
>>>>>
>>>>>
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