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

[Hendrik Schreiber]

On Mon, 8 Nov 2021 18:31:11 GMT, Anthony Vanelverdinghe <duke at openjdk.java.net> 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 90:
> 
>> 88:  * public class CleaningExample implements AutoCloseable {
>> 89:  *        // A cleaner, preferably one shared within a library
>> 90:  *        private static final Cleaner cleaner = Cleaner.create();
> 
> Now the code (creating a private instance) goes against what the comment advises (using a shared instance), doesn't it?

You have a point.

BUT, at least it's a working example and not some pseudo code. We do want to move to working example code long term, don't we?

When I see <cleaner>, I'm just wondering what those <> type operators are good for here...

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