RFR: 8302603: Use Set.of in java.nio.charset.Charset

[Alan Bateman]

On Wed, 15 Feb 2023 19:25:20 GMT, Naoto Sato <naoto at openjdk.org> wrote:

>> A small patch, using `Set.of` instead of `Collections.unmodifiableSet()` of `Charset#aliasSet`.
>> 
>> The alias should not be null, and the aliasSet is an immutable copy, so it is safe to use `Set.of`.
>> 
>> I have investigated all charsets, most of charsets have no more than 4 aliases, and the maximum is only 17.
>> 
>> In this case, the performance difference between immutable sets and HashSet can be ignored, and the memory footprint of immutable sets is smaller.
>> 
>> I need someone to help me open an Issue on JBS. Thank you very much.
>
> Good cleanup. Filed an issue: https://bugs.openjdk.org/browse/JDK-8302603

I can sponsor but I'm giving maintainers in this area, e.g. @naotoj, a chance to comment.

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PR: https://git.openjdk.org/jdk/pull/12570