[concurrency-interest] Significance of volatile for Objects

Dhanji R. Prasanna dhanji at gmail.com
Fri Mar 7 07:18:49 EST 2008


On Fri, Mar 7, 2008 at 10:19 PM, Pavitar Singh <pavitar at pramati.com> wrote:

> Hi,
>
> Thanks for your explanations.
>
> When i read JMM about Happens Before Relationships:
>
> It says:
>
> A write to a volatile field happens before every subsequent read of that
> volatile.
>
> But then doing operation on HashMap like put. It doesnt mean write to the
> volatile field.Siimilarly a get shouldnt mean read from volatile.Is it
> correct or i am missing something here.


Correct, the volatile field holds a reference to a hashmap, but reads and
writes to the hashmap itself are subject to its own synchronization
concerns. Hence, synchronized and ConcurrentHashMap.

Dhanji.
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