Draft JEP Announcement: "Computed Constants"

[forax at univ-mlv.fr]

> From: "Brian Goetz" <brian.goetz at oracle.com>
> To: "Remi Forax" <forax at univ-mlv.fr>, "Per-Ake Minborg"
> <per-ake.minborg at oracle.com>
> Cc: "leyden-dev" <leyden-dev at openjdk.org>, "John Rose" <john.r.rose at oracle.com>
> Sent: Thursday, July 27, 2023 6:23:01 PM
> Subject: Re: Draft JEP Announcement: "Computed Constants"

> As Maurizio said, this JEP is a refinement of ideas that were initially explored
> in the "lazy statics" JEP. In a way, this JEP reveals the "lazy statics" JEP as
> skipping a step, jumping to a language and VM when much of the benefit can be
> achieved by a libraries approach. It is possible that at some point, after
> suitable progress and validation, we may decide to take the step of pushing it
> further into the language/VM, but we've made the deliberate choice to push such
> steps into the future.

> In the meantime, there is no reason we cannot have multiple "inconsistent" draft
> or candidate JEPs, so there is no need to "merge" anything right now.
Here is my counter-proposal, use a @Lazy annotation to mark the static final field and requires the static final fields to be initialized by a static method. 

With the Logger example, it becomes 

class Bar { 
// 1. Declare a computed constant value, it has to be initialized by a static method 
private static final @Lazy Logger LOGGER = initLogger(); 

// 2. Initialize the value 
private static Logger initLogger() { 
return Logger.getLogger("com.foo.Bar"); 
} 
} 

You have exactly the same information, it's easier for a class rewriter than the computed constant proposal and a compiler guy and then a VM guy can also work on it. 
And obvisouly, it's a backward compatible change. 

Rémi 

> On 7/27/2023 12:09 PM, Remi Forax wrote:

>> Hello,
>> Are you aware of the lazy static final fields proposal ?
>> [ https://bugs.openjdk.org/browse/JDK-8209964 |
>> https://bugs.openjdk.org/browse/JDK-8209964 ]

>> In think both proposals should be merged.

>> Rémi

>>> From: "Per-Ake Minborg" [ mailto:per-ake.minborg at oracle.com |
>>> <per-ake.minborg at oracle.com> ]
>>> To: "leyden-dev" [ mailto:leyden-dev at openjdk.org | <leyden-dev at openjdk.org> ]
>>> Sent: Thursday, July 27, 2023 5:52:46 PM
>>> Subject: Draft JEP Announcement: "Computed Constants"

>>> Hi all,

>>> Maurizio and I have drafted a JEP for computed constants, which are
>>> immutable value holders that are initialized at most once. They offer
>>> the performance and safety benefits of final fields while offering
>>> greater flexibility as to the timing of initialization. In the
>>> context of Leyden, they could be one basis for shifting computation
>>> both forward and backward in time.

>>> The draft is here: [ https://openjdk.org/jeps/8312611 |
>>> https://openjdk.org/jeps/8312611 ]

>>> Now that the Leyden repo is open, I’ll publish the prototype code to a
>>> new branch there shortly.

>>> Comments are welcome!

>>> Best, Per
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