RFR: 8276700: Improve java.lang.ref.Cleaner javadocs

[Hendrik Schreiber]

On Fri, 5 Nov 2021 22:22:12 GMT, Mandy Chung <mchung at openjdk.org> wrote:

>> Trivial improvement.
>> 
>> Explicitly show how to create a `Cleaner` instance using `Cleaner.create()`.
>> Repeat (again) in the code example that the `State` `Runnable `should be implemented as static class and not reference the instance to be cleaned, to make the point even more clear to those people who never read the javadoc *prose*.
>> 
>> I have signed the OCA a while back as [hschreiber](https://openjdk.java.net/census#hschreiber).
>
> src/java.base/share/classes/java/lang/ref/Cleaner.java line 93:
> 
>> 91:  *
>> 92:  *        // Static state class, capturing information necessary for
>> 93:  *        // cleanup, but no reference to the instance being cleaned
> 
> Suggestion:
> 
>  *        // State class captures information necessary for cleanup.
>  *        // It must hold no reference to the instance being cleaned
>  *        // and therefore it is a static inner class in this CleaningExample.
> 
> 
> Would this be clearer?

I don't believe so. `no reference to the instance being cleaned` is the essential part (to me).

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PR: https://git.openjdk.java.net/jdk/pull/6076