Ad removing finalize eventually (Re: JEP 411 Headaches: Instrumenting private methods in the JDK for authorization checkpoints.

[Roger Riggs]

Hi Rony,

Also take a look at the java.lang.ref.Cleaner 
<https://docs.oracle.com/en/java/javase/11/docs/api/java.base/java/lang/ref/Cleaner.html>[1] 
added to in JDK 9.
It is designed as a replacement for finalization; it uses the 
PhantomReferences to register cleanup actions.

Regards, Roger

[1] 
https://docs.oracle.com/en/java/javase/11/docs/api/java.base/java/lang/ref/Cleaner.html

On 7/27/21 9:42 AM, Rony G. Flatscher wrote:
> Peter,
>
> On 27.07.2021 13:24, Peter Firmstone wrote:
>> PhantomReference
>>
>> like this:
>>
>> https://github.com/pfirmstone/JGDMS/blob/trunk/JGDMS/jgdms-collections/src/main/java/org/apache/river/concurrent/ReferenceProcessor.java
>>
> thank you very much for the pointer!
>
> ---rony
>
>> On 27/07/2021 8:01 pm, Rony G. Flatscher wrote:
>>> Ad Alan's remark about eventually removing finalize in this thread:
>>>
>>> On 25.07.2021 16:44, Alan Bateman wrote:
>>>
>>> ... cut ...
>>>> That said, there is strong desire to eventually remove finalization too. Finalization was
>>>> deprecated several years ago and the Java platform defines APIs that provide much more flexible
>>>> and efficient ways do run cleanup actions when an object becomes unreachable. So another
>>>> multi-year/multi-release effort to remove a problematic feature, just nothing to do with this JEP.
>>> ... cut ...
>>>
>>> A question: what alternatives are you thinking of?
>>>
>>> Background of the question: in an ooRexx-Java bridge for each Java object an ooRexx peer object gets
>>> created and needs to exist as long as the Java object exists. Once the Java object gets garbage
>>> collected the ooRexx peer object needs to be freed as well. The bridge between ooRexx (an
>>> interpreted, message based, dynamically typed language) and Java is realized via JNI. Currently
>>> (actually since 20 years) on the Java side the finalize method gets employed to signal to ooRexx
>>> that its ooRexx peer object needs to be removed.
>>>
>>> So when you think of removing finalize and think of replacements for it, is there already a
>>> replacement devised which can be used for determining that a Java "object became unreachable"/is not
>>> referred to anymore/about to be garbage collected (or not being interacted with anymore for good)
>>> and be able to communicate that fact/event? What would that be? Are there already discussions, ideas
>>> about this somewhere?
>>>
>>> ---rony
>>>
>>> P.S.: I remember the comment back then that finalize although deprecated for use (not for removal)
>>> for Java programs will not be removed as such use cases as described above need to use it.