RFR: 8171373: Reduce copying during initialization of ModuleHashes

[Claes Redestad]

Chris, Mandy,

thanks for reviewing!

I've made nameToHash final and added a comment, updated in place.

I'll push this tomorrow unless I hear any objections.

/Claes

On 2016-12-16 18:52, Mandy Chung wrote:
>
>> On Dec 16, 2016, at 8:00 AM, Claes Redestad <claes.redestad at oracle.com> wrote:
>>
>> Hi,
>>
>> recent changes to split out ModuleHashes from ModuleDescriptor caused a small/tiny increase in HashMap creation, resize and copying:
>>
>> Webrev: http://cr.openjdk.java.net/~redestad/8171373/webrev.01/
>> Bug: https://bugs.openjdk.java.net/browse/JDK-8171373
>
> I like the optimization for one single module (i.e. java.base) containing the module hashes which is the common case.
>
> Can you add a comment in SystemModuleFinder about the common case and avoid creating a new HashMap unless there is more than one module containing ModuleHashes.
>
> Builder::nameToHash can now be final.
>
> Mandy
>