RFR: 8263903: Use Cleaner instead of finalize to auto stop Timer thread [v3]

[Alan Bateman]

On Tue, 23 Mar 2021 01:03:55 GMT, Kim Barrett <kbarrett at openjdk.org> wrote:

>> Please review this change to java.util.Timer, replacing the use of deprecated finalization-based cleanup with use of java.lang.ref.Cleaner.
>> 
>> In addition, Timer.cancel now cancels any later execution of the the no longer relevant cleanup.
>> 
>> Testing:
>> mach5 tier1
>> New AutoStop test verifies the specified cleanup behavior.
>> (There are existing tests involving Timer.cancel.)
>
> Kim Barrett has updated the pull request incrementally with one additional commit since the last revision:
> 
>   make ThreadReaper constructor non-public

Marked as reviewed by alanb (Reviewer).

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PR: https://git.openjdk.java.net/jdk/pull/3106