[concurrency-interest] jsr166y classes now in jdk7m5
alexdmiller at yahoo.com
Sun Nov 15 15:26:08 EST 2009
Glad to see stuff hitting the JDK 7 repo. I'm guessing from this message that stuff like ConcurrentReferenceHashMap / MapMaker or the concurrent LRU work won't make it into JDK 7?
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> 1. jsr166y classes now in jdk7m5 (Doug Lea)
> Message: 1
> Date: Sun, 15 Nov 2009 09:10:38 -0500
> From: Doug Lea
> Subject: [concurrency-interest] jsr166y classes now in jdk7m5
> To: "concurrency-interest at cs.oswego.edu"
> Message-ID: <4B000BDE.1080802 at cs.oswego.edu>
> Content-Type: text/plain; charset=ISO-8859-1; format=flowed
> ForkJoin, Phasers, and TransferQueues are now incorporated
> in package java.util.concurrent in the latest JDK7 snapshots,
> downloadable at http://download.java.net/jdk7/m5/
> Please try these out and let us know of any problems.
> We will still maintain JDK6-compatible versions
> for the indefinite future in package jsr166y (see
> This should also make it easier for those using these
> classes from other languages and frameworks. You can
> rely on jsr166y versions until JDK7 release, although at
> that point you'll probably need to make a visible
> switch-over to j.u.c versions. Further, it is likely
> that at some point we will make changes that
> rely on other JDK7 features.
> Especially during this transition, please be careful
> with "import" statements in sources --
> avoiding "*" imports from either jsr166y or
> java.util.concurrent, to avoid compile-time
> or run-time errors about name clashes by users
> running JDK7 snapshots.
> In general, changes show up in our jsr166y
> and j.u.c CVS before they appear in openjdk or
> Sun JDK7 snapshot releases.
> There already a few small improvements there vs
> jdk7m5 versions. We plan to occasionally commit
> small batches of them into openjdk.
> We don't have plans for JDK5 backports. There
> are a couple of performance-critical constructions
> in these classes that rely on JDK6 intrinsics.
> They are costly to emulate in JDK5, so it is
> not clear how useful they would be.
> This also impacts current IBM Java (J9) users even in
> JDK6, because it doesn't support some of the
> hotspot intrinsics. I understand that this will
> be addressed in an IBM JDK6 update.
> More generally, we are hoping to find a way to
> ensure compatibility in the future across JVMs for
> these JDK-internal non-public APIs (that have
> escaped standardization), to avoid future problems
> along these lines.
> The main known remaining jsr166-related task for JDK7 is
> to try to make good on schemes that avoid the need
> for the controversial Fences API by improving
> AtomicXUpdater APIs and somehow removing their overhead.
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> End of Concurrency-interest Digest, Vol 58, Issue 8
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