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

[David M. Lloyd]

Also be aware that JBMAR has specific optimizations for the JDK empty 
collections - they are represented by a single byte in the stream.

On 10/19/2012 11:28 AM, Dan Berindei wrote:
> Galder, what JDK are you using? 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
>
> 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.
>
> Cheers
> Dan
>
>
> On Fri, Oct 19, 2012 at 5:50 PM, Vladimir Blagojevic
> <vblagoje at redhat.com <mailto: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 <mailto:galder at redhat.com>
>      > twitter.com/galderz <http://twitter.com/galderz>
>      >
>      > Project Lead, Escalante
>      > http://escalante.io
>      >
>      > Engineer, Infinispan
>      > http://infinispan.org
>      >
>      >
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