RFR: 8302603: Use Set.of in java.nio.charset.Charset [v3]

[Alan Bateman]

On Mon, 20 Feb 2023 18:34:52 GMT, Glavo <duke 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.
>
> Glavo has updated the pull request incrementally with one additional commit since the last revision:
> 
>   update

Marked as reviewed by alanb (Reviewer).

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