RFR: 8351565: Implement JEP 502: Stable Values (Preview) [v25]

[Per Minborg]

On Wed, 2 Apr 2025 09:17:23 GMT, Per Minborg <pminborg at openjdk.org> wrote:

>> src/java.base/share/classes/java/lang/StableValue.java line 95:
>> 
>>> 93:  * <p>
>>> 94:  * Note that the holder value can only be set at most once.
>>> 95:  * In the example above, the {@code logger} field is declared {@code final} which is
>> 
>> This is not 100% true -- a final non-static field is not treated as a constant by the VM (at least not yet). Again, I suggest to keep this discussion focused on the fact that `logger` is a `final` stable value field. The holder is created eagerly, but the _content_ is initialized lazily (in the `getLogger` method). So, same similar to `final` (can only be set once) -- but more flexible.
>
> Now that we have removed the VM-specific handling of fields declared as `StableValue`, this is true. I will take a look at improving the wording.

I've used `static` fields now to get out of the muddy waters of trusted final fields, records etc.

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

PR Review Comment: https://git.openjdk.org/jdk/pull/23972#discussion_r2024641249