Path: csiph.com!eternal-september.org!feeder.eternal-september.org!news.eternal-september.org!.POSTED!not-for-mail
From: Andreas Leitgeb <avl@logic.at>
Newsgroups: comp.lang.java.programmer
Subject: Re: What's the best way to make a cross string set?
Date: Thu, 3 Aug 2017 14:33:23 -0000 (UTC)
Organization: A noiseless patient Spider
Lines: 42
Message-ID: <slrnoo6d9a.o2q.avl@logic.at>
References: <6f9ff338-1944-4b64-83b8-4a921ce57a89@googlegroups.com> <olfv7c$8l3$3@Gaia.teknon.de> <d4c8c823-5603-4b80-be33-629d8d307faf@googlegroups.com> <olg9jv$8ct$1@dont-email.me> <69ec0210-e2a0-4823-98f0-8fc72e5c5db9@googlegroups.com> <olq4mi$ch1$1@dont-email.me> <f6d72507-62a9-4442-b7c9-cb47c9ed60fe@googlegroups.com> <3664ab4d-9619-43d0-9535-1ce7ab4d4438@googlegroups.com> <a107955f-5c2c-4e0e-8033-4009d7eb26fd@googlegroups.com> <slrnoo36mh.o2q.avl@logic.at> <ab4d1e2d-baae-488d-a6a3-9e0c31037c4d@googlegroups.com>
Reply-To: avl@logic.at
Injection-Date: Thu, 3 Aug 2017 14:33:23 -0000 (UTC)
Injection-Info: mx02.eternal-september.org; posting-host="3372b44961abf9e24369633da1e6adcb"; logging-data="9393"; mail-complaints-to="abuse@eternal-september.org";	posting-account="U2FsdGVkX18YSuRTqInVosbKUe5tkeP7"
User-Agent: slrn/1.0.2 (Linux)
Cancel-Lock: sha1:wGG59E/Yd5p809E1H3b21wBAldI=
Xref: csiph.com comp.lang.java.programmer:37054

Eric Douglas <e.d.programmer@gmail.com> wrote:
> On Wednesday, August 2, 2017 at 5:27:01 AM UTC-4, Andreas Leitgeb wrote:
>> Are you sure that you had to change it?  The <?> could be just fine
>> in many cases. It just means that the generics class itself doesn't
>> give a dime about it's parameter type or any restrictions on it.
>> It's certainly *not* just eclipse saying "dunno".
> Yes, for instance I have a method declared as
>      protected Comparable<Object> getCompareValue() {
> I call this method from
>      final Comparable compareMe = getCompareValue();
> Eclipse auto-changes this to
>      final Comparable<Comparable<?>> compareMe = getCompareValue();

I cannot reproduce that with my (oldish) Eclipse 3.8.1 here.
With "add type arguments" it seems to just add "<?>", and
with "Change type to Comparable<Object>" it obviously changes
it to Comparable<Object>, but I didn't get it to change it to
Comparable<Comparable<?>>.

Generally, Comparable<Object> makes little sense based on what 
Comparable is designed for, namely as an anti-symmetric operation.
I was even surprised that Comparable does not restrict its type
argument, but then I remembered that were it defined like
  Comparable<T extends Comparable<T>>
then it wouldn't be possible to use it with anonymous classes.

Maybe a newer eclipse than mine has some hardcoded "knowledge"
of Comparable and therefore tries to make something more sensible
than the locked-down interface would imply.

> If I just fix it to match it works fine.
>      final Comparable<Object> compareMe = getCompareValue();

Consider changing already getCompareValue() to return something
better than Comparable<Object>.

> Somehow Eclipse didn't know it needed to be Comparable<Object>
> even though it auto-added the <Object> to the return value on
> the method.

That might have been deduced from your implementation of getCompareValue().