RFR: 8297276: Remove thread text from Subject.current

[Weijun Wang]

On Wed, 23 Nov 2022 12:35:17 GMT, Alan Bateman <alanb at openjdk.org> wrote:

>> With the introduction of Virtual Threads, the current subject is no longer guaranteed to be inherited in a new thread. Remove this requirement until we find another way to implement `Subject::current`.
>
> Just re-reading the javadoc for Subject.callAs. It doesn't say anything about inheritance so there shouldn't be any expectation that Subject is inherited, so I think the change proposed here is okay. For another PR but I think the callAs javadoc could say a bit more about the Subject being set for the bounded execution of the given task. When the task completes, the current Subject is null or reverts to its previous value in the current thread.

@AlanBateman You are right. The `callAs` method is very short and only mentions "the current subject". My original idea is to describe everything about what "the current subject" means inside the `current()` method, which now talks about how it's set and reset. Do you think it's clearer to duplicate some of these words in `callAs` as well? Both the two methods currently have a `@see` pointing to the other.

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PR: https://git.openjdk.org/jdk/pull/11292