RFR: 8302108: Clean up placeholder supername code [v2]

[Coleen Phillimore]

On Mon, 13 Feb 2023 19:20:03 GMT, Ioi Lam <iklam at openjdk.org> wrote:

>> Coleen Phillimore has updated the pull request with a new target base due to a merge or a rebase. The pull request now contains three commits:
>> 
>>  - Fix test for cleanup for nulling out supername when no longer used.
>>  - Merge branch 'master' into placeholder-cleanup
>>  - 8302108: Clean up placeholder supername code
>
> src/hotspot/share/classfile/placeholders.hpp line 102:
> 
>> 100:   bool remove_seen_thread(JavaThread* thread, PlaceholderTable::classloadAction action);
>> 101: 
>> 102:   SeenThread*        superThreadQ()        const { return _superThreadQ; }
> 
> If you just want to change these function to private, instead of moving them, I would suggest adding `private:` and `public:` keywords around them. That way we can limit the delta.

I really wanted them moved to the section of the class where the other private methods are.  This class isn't so overgrown that we need to keep switching from private to public, and I want the public methods to be together.
Java is nice in that you can have 'private' and 'public' keywords on each function, but I'd still like to keep the public ones together.

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PR: https://git.openjdk.org/jdk/pull/12495