RFR 8005704: Update ConcurrentHashMap to v8
martinrb at google.com
Wed May 29 04:29:20 UTC 2013
On Tue, May 28, 2013 at 9:00 PM, David Holmes <david.holmes at oracle.com>wrote:
> On 29/05/2013 5:53 AM, Martin Buchholz wrote:
>> Is atomicity part of the contract of ConcurrentMap.getOrDefault?
>> Currently, it doesn't say.
>> Actually, there are two possible guarantees it could make - whether the
>> default implementation ConcurrentMap.getOrDefault is atomic (when the map
>> does not accept nulls) and whether subclasses that override getOrDefault
>> must make this guarantee.
> I want to re-examine the new methods that ConcurrentMap is inheriting from
> Map because I think more statements regarding concurrency properties are
> required. This included getOrDefault even though overridden.
>> Curiously, ConcurrentMap doesn't guarantee that get() is atomic. Perhaps
>> it should?
> Only composite operations (those that could expressed as a sequence of
> other operations) need an atomicity guarantee. Operations like get() simply
> need to be thread-safe.
You're right. Let me rephrase:
Curiously, ConcurrentMap doesn't guarantee that get() is thread-safe, or
that a ConcurrentMap can be used from multiple threads. Perhaps it should?
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