[10] RFR: 8184665: Skip name and alias checks for standard Charsets

[Claes Redestad]

Hi,

in this case the code isn't really fragile, since two equal but not
identical Strings will end up with the same Charset, so there's no
*real* surprises to be had (only a tiny performance loss that isn't
really consequential except for startup).

So: I did use == mostly to be consistent with StandardCharsets, although
it is also a gain by a few bytecodes less executed on startup. We could
change to equals in both places as well if consistency is all that
matters, but since this is established behavior I'd rather use ==
in the new place, and add a comment about why it's valid. Reasonable?

I'll add a regression test to test these standard Charsets are kept
well-behaved, as per Sherman's comment.

Thanks!

/Claes

On 2017-07-14 20:08, Roger Riggs wrote:
> Hi Remi,
>
> Point taken about consistency.
> I'm concerned about code that is unnecessarily fragile due to 
> unnecessary and unexpected optimizations.
>
> $.02, Roger
>
>
> On 7/14/2017 2:01 PM, Remi Forax wrote:
>> I do not like the equals in the constructor of Charset given that in 
>> StandardCharsets, == is used.
>>
>> I think the constructor of Charset should use == and a comment should 
>> be added explaining why it's valid to use == like in StandardCharsets.
>>
>> cheers,
>> Rémi
>>
>> ----- Mail original -----
>>> De: "Roger Riggs" <Roger.Riggs at Oracle.com>
>>> À: "core-libs-dev" <core-libs-dev at openjdk.java.net>
>>> Envoyé: Vendredi 14 Juillet 2017 19:12:09
>>> Objet: Re: [10] RFR: 8184665: Skip name and alias checks for 
>>> standard Charsets
>>> +1,
>>>
>>> Thanks, Roger
>>>
>>> On 7/14/2017 1:03 PM, Claes Redestad wrote:
>>>> Hi Roger,
>>>>
>>>> On 2017-07-14 18:25, Roger Riggs wrote:
>>>>> Hi Claes,
>>>>>
>>>>> Using == with references always looks a bit suspicious in the source
>>>>> code, especially strings.
>>>>> Since the first thing in equals() is the identity check, I'd suggest
>>>>> using .equals for the comparisons.
>>>> Sure, there's no significant performance difference, even in
>>>> interpreted mode:
>>>>
>>>> http://cr.openjdk.java.net/~redestad/8184665/jdk.01/
>>>>
>>>> /Claes
>