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

[Aleksey Shipilev]

On Fri, 22 Oct 2021 08:03:34 GMT, Hendrik Schreiber <hschreiber 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).

Submitted the RFE for it. Please change the PR title to "8276700: Improve java.lang.ref.Cleaner javadocs" to let bots hook it up.

-------------

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