[infinispan-dev] Avoid Collections.emptySet() / emptyMap() / emptyList

[Dan Berindei]

On Mon, Oct 22, 2012 at 9:25 AM, Galder Zamarreño <galder at redhat.com> wrote:

>
> On Oct 19, 2012, at 6:28 PM, Dan Berindei <dan.berindei at gmail.com> wrote:
>
> > Galder, what JDK are you using?
>
> java version "1.6.0_35"
> Java(TM) SE Runtime Environment (build 1.6.0_35-b10-428-11M3811)
> Java HotSpot(TM) 64-Bit Server VM (build 20.10-b01-428, mixed mode)
>
> > OpenJDK 1.7 uses EmptyIterator.EMPTY_ITERATOR since 2007:
> >
> >
> http://hg.openjdk.java.net/jdk7/jdk7/jdk/annotate/37a05a11f281/src/share/classes/java/util/Collections.java
>
> Good that the figured out this is non-sense.
>
> > I don't have JDK 1.6 sources on hand to check, but I don't think it's
> worth optimizing for such an old version anyway.
>
> Why not? We support JDK 1.6, so nothing stops them from running it.
>
> Until we baseline on JDK7 (or 8), I'd leave it in.
>
>
My point was that it is a really big change, and further it imposes a
burden on anyone writing code with collections in Infinispan. I'm sure we
will spend non-trivial amounts of time during reviews pointing out places
there the author should have used InfinispanCollections instead of
Collections...

I would be willing to go for it if a benchmark showed a significant
increase in performance after the change, but you didn't mention any
benchmarks, so I guessed that you didn't see a big difference...


>
> > Cheers
> > Dan
> >
> >
> > On Fri, Oct 19, 2012 at 5:50 PM, Vladimir Blagojevic <
> vblagoje at redhat.com> wrote:
> > Cool! Did not know about this! Is this original idea or others are
> > already doing this?
> > On 12-10-19 8:31 AM, Galder Zamarreño wrote:
> > > Hi all,
> > >
> > > Re:
> https://github.com/galderz/infinispan/commit/0609207d13216de81d77ff51dc20652ce270c635
> > >
> > > Please avoid using these JDK methods where possible. I've created
> alternative versions in InfinispanCollections util class that provide a
> better implementation.
> > >
> > > The problem with the JDK versions is that even if these collections
> are immutable, if you wanna iterate them (i.e. for(X : emptySet) ), they'll
> create a brand new Iterator every time they're looped, and that generates
> useless garbage.
> > >
> > > The InfinispanCollections versions of emptyX will return a constant
> singleton iterator which avoids this problem, and avoids the need for
> client code to check if the collection is empty before looping.
> > >
> > > Cheers,
> > > --
> > > Galder Zamarreño
> > > galder at redhat.com
> > > twitter.com/galderz
> > >
> > > Project Lead, Escalante
> > > http://escalante.io
> > >
> > > Engineer, Infinispan
> > > http://infinispan.org
> > >
>
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