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

[Adrian Cole]

Learned something new!

---------- Forwarded message ----------
From: "Galder Zamarreño" <gal...@redhat.com>
Date: Oct 19, 2012 5:32 AM
Subject: [infinispan-dev] Avoid Collections.emptySet() / emptyMap() / emptyList
To: "infinispan -Dev List" <infinis...@lists.jboss.org>

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
gal...@redhat.com
twitter.com/galderz

Project Lead, Escalante
http://escalante.io

Engineer, Infinispan
http://infinispan.org


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[Tim Peierls]

I can't find any sign that Guava is doing the same, but perhaps they've measured and found that the extra garbage is so readily reclaimed that it isn't worth the extra code complexity.

--tim

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[Andrew Gaul]

I tested against Guava 13.0.1 and it does not create an unneeded object.  I will submit a pull request to clean up jclouds.

[Tim Peierls]

What clean-up is needed if Guava doesn't create any unneeded objects?

To view this discussion on the web visit https://groups.google.com/d/msg/jclouds-dev/-/mP6Ow_RYxIgJ.

[Adrian Cole]

I'm guessing there are places we use Collections vs ImmutableX.of()

-A