On Oct 16, 2013, at 6:41 AM, David Holmes <[email protected]> wrote:
> Okay you have incited me to throw in my 2c :) I think the CME issue has been
> raised a number of times in the past (and if the below doesn't agree with
> what I've said in the past Hey! It's a brand new day! ;-) )
>
> But first, Mike the missing spaces are creeping back in "if(xxx)" :)
>
> For Map I don't think looking for external concurrent modification and
> throwing CME is necessary or worthwhile. These are not thread-safe methods.
> That covers:
> - remove, replace
>
> and it implies that putIfAbsent should not check for or throw CME.
>
> For compute* and merge it is possible that the computation function modifies
> the Map - unlikely perhaps but possible - so CME here seems more reasonable.
> (As for forEach, replaceAll etc.)
>
> I fully agree with removing the retry loops in these non-concurrent
> implementations.
>
> That said it makes ConcurrentMap somewhat different to Map as it never throws
> CME even if it was an internal mutation.
>
HashMap.compute*/merge methods do not throw CME either. I suppose those methods
could and do so beyond that of only the entry under computation. I think this
really points to the fact that, for non-traversal, only concrete
implementations are capable of reliably detecting a CME and therefore it's best
to leave it up to those implementations should they choose to do so.
Paul.
> Aside: do you still need to re-list every unchecked exception when overriding
> (i.e. @throws foo {@inheritDoc}) to get them to show up in the subtype docs?
> I can't tell if this has been forgotten or whether the ConcurrentMap methods
> truly will never throw such exceptions.
>
> Cheers,
> David
> -----
