[concurrency-interest] jsr166y classes now in jdk7m5

Doug Lea dl at cs.oswego.edu
Sun Nov 15 16:51:43 EST 2009

Alex Miller wrote:
> I'm guessing from this message
> that stuff like ConcurrentReferenceHashMap / MapMaker or the concurrent LRU
> work won't make it into JDK 7?

Hard to say, since we don't know how far out Java7/JDK7 will
be. The two main concerns are:
* Most caches would benefit from dependent weak reference
(aka ephemeron) JVM support, which is not currently planned.
* I don't think we have much consensus yet on which replacement
policies (pseudo-LRU etc) are amenable to standardized
library support and/or how to allow plugging in more
specialized forms like those that Bob Lee, Kevin Bourrillion,
and friends have been working on for Google collections.

In some analogous situations, we've settled on
the idea that providing something is better than nothing.
But in this case just putting out something hits various
API design controversies, like should a "cached function"
act more like a Map or a Function. Oh, wait, we don't
even have a Function API and may never want/need one if
Java ever supports function-types. And several more along
these lines. So for the time being I'm hoping that
people will be content to continue to use pre-standardized
cache components out there until some of these various JVM,
algorithmic, and API issues become better resolved.


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