bye stable values, enter lazy constants

[Remi Forax]

----- Original Message -----
> From: "Maurizio Cimadamore" <maurizio.cimadamore at oracle.com>
> To: "leyden-dev" <leyden-dev at openjdk.org>
> Sent: Monday, September 29, 2025 11:15:36 AM
> Subject: bye stable values, enter lazy constants

> Hi all,
> Per and I have been completed another round of preview of the Stable
> Value API. As you might have noticed, the name changed (again!) to
> LazyConstant 🙂
> 
> https://openjdk.org/jeps/526
> 
> In many ways, the new API is more similar to the old ComputedConstant
> API, as the imperative methods are gone: the only way to create a lazy
> constant is by providing a lambda expression at construction.
> 
> The reason behind the change is that, after performing extensive
> experiments with the StableValue API, we have learned that:
> 
> * Most use cases could be expressed with a caching supplier. This meant
> that in most cases developers never needed to interact with StableValue
> -- which seemed odd.
> * For low-level cases, the imperative API we provided was not low-level
> enough, as it still added significant synchronization and boxing costs.
> This made the API unsuitable to use in performance critical code (such
> as the ClassFile API).
> 
> For these reasons we have decided to shift the design center of the API
> back to the most common, functional use cases, which led us to this
> simpler API. That said, the quest for a more fundamental building block
> is not over: we now have a clearer idea on how to expose "stable" access
> to regular fields/array elements, using a _new_ var handle access mode.
> Initial experiments look indeed promising: such an approach doesn't
> require the allocation of intermediate abstractions, and allows clients
> to decide if they want to pay for synchronization or not.

+1 for a new VarHandle access mode !

> 
> As always, we are very thankful for all the feedback we have received so
> far, and we look forward for some more!
> 
> Cheers
> Maurizio

regards,
Rémi