On Mon, 8 Nov 2021 19:40:20 GMT, Hendrik Schreiber <hschrei...@openjdk.org>
wrote:
>> 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...
A cleaner can/should be shared within some scope and purpose, in this case the
example class .
Each cleaner has a dedicated Thread so its not a lightweight object and should
not be proliferated.
(Loom may be able to use Virtual Threads).
The reasons to not share are a Cleaner are based on possible interference
between the cleanup callbacks.
If they share a thread and are non-trivial, it might slow other cleaners. If
the cleaner is created and shared
for a particular purpose it will share the thread resource and still be
efficient.
-------------
PR: https://git.openjdk.java.net/jdk/pull/6076
