[concurrency-interest] question about ConcurrentHashMapV8.RemappingFunction

Doug Lea dl at cs.oswego.edu
Fri Jun 29 09:45:24 EDT 2012


On 06/29/12 09:14, Kasper Nielsen wrote:
> Are the various compute methods only going to be available on CHM?
> I mean letting null indicate a removal (or something else) makes it
> impossible to introduce them
> later on any kind of maps that allow null values.

As mentioned in another thread, these methods can/should also be
added to ConcurrentSkipListMap. And someday there may be some
good opportunity to create an interface covering them and others.
But all reasonable concurrent maps do not support null values:
It would be impossible to distinguish null values from absence
of mapping -- the sequential "m.get(k) == null && !m.containsKey(k)"
idiom does not apply. So future concurrent maps should be able to
support these methods as well.

-Doug


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