Collections.emptyList().sort() does nothing

[Vitaly Davidovich]

On Wed, Nov 15, 2017 at 5:21 AM Andrej Golovnin <andrej.golovnin at gmail.com>
wrote:

> > On 15/11/17 10:03, Andrej Golovnin wrote:
> >> I think we would need to write ugly code in any case as Java 9 has now
> >> two empty list implementations: Collections.emptyList() and List.of().
> >>
> >> Collections.emptyList().sort() does not throw an exception.
> >>
> >> List.of().sort() throws an exception.
> >
> > Well, that's a bug.  Sorting an empty list is perfectly valid, and
> application
> > programmers shouldn't have to special-case it.
>
> I don't think so. I would say that the implementation of
> Collections.emptyList() is broken. Collections.emptyList() and
> List.of() are not only empty lists. They are also immutable per
> specification.
>
> Here is another example of an unsortable empty list:
>
> Collections.unmodifiableList(Collections.emptyList()).sort() throws an
> exception.

One can argue that since those are empty by construction/design, sorting
them is not a bug.  That’s different from, say, trying to sort an
unmodifiable list that happens to be empty and not failing in that case.

>From a user’s perspective, I agree it’s annoying to have to special case
these.  This is particularly so because immutability is not expressed in
the types or type system.

>
>
> >
> > --
> > Andrew Haley
> > Java Platform Lead Engineer
> > Red Hat UK Ltd. <https://www.redhat.com>
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