RFR 8005704: Update ConcurrentHashMap to v8

[Martin Buchholz]

On Tue, May 28, 2013 at 9:00 PM, David Holmes <david.holmes at oracle.com>wrote:

> Martin,
>
>
> 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.
>
>
Agreed.


>
>  ---
>>
>> 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?