from computed constants to stable values

[Maurizio Cimadamore]

Hi all,
Per and I have been busy polishing the Computed Constant API. So much so 
that it has now changed name to Stable Value API :-)

https://openjdk.org/jeps/502

The goal is still to provide a safe API around JVM's @Stable value 
annotation. But, as we experimented with the old API, we realized that 
its "lambda-oriented" design, while good, was too restrictive when 
clients wanted to "set" the computed constant in a more imperative fashion.

In the new Stable Value API, stable values are created unset. They can 
be set imperatively, or more functionally using a method similar to 
Map::computeIfAbsent. If you squint, the old computed constants have not 
disappeared: a computed constant can be expressed as a supplier that 
wraps a stable value -- we call such a supplier a "stable supplier".

Per's talk at Devoxx 2024 is a good companion to the new JEP, with lots 
of interesting live examples:

https://www.youtube.com/watch?v=3fXHrK3yV9w

Let us know what you think!

Cheers
Maurizio