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

[Manik Surtani]

On 22 Oct 2012, at 09:13, Dan Berindei <dan.berindei at gmail.com> wrote:

> 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,

Why?  The patch was trivial.  Implementing it is easy, and then doing a search and replace on the codebase again resulted in a pretty small patch.

> and further it imposes a burden on anyone writing code with collections in Infinispan.

Is it that hard for a reviewer to spot?  :)  Maybe even write a script to check and warn for this.

> 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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--
Manik Surtani
manik at jboss.org
twitter.com/maniksurtani

Platform Architect, JBoss Data Grid
http://red.ht/data-grid

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