RFR: 8263903: Use Cleaner instead of finalize to auto stop Timer thread [v2]

[Kim Barrett]

On Mon, 22 Mar 2021 07:15:24 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:
> 
>   dholmes review

test/jdk/java/util/Timer/AutoStop.java line 27:

> 25:  * @test
> 26:  * @bug 8263903
> 27:  * @requires vm.gc != "Epsilon"

I added the `@requires` late in dev/test and used the wrong test.

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