[External] : Re: Feedback about LazyConstants API (JEP526)
Red IO
redio.development at gmail.com
Tue Dec 9 11:37:23 UTC 2025
You can implement orElse in combination with a test function that returns a
boolean rather the value is there already. I don't see orElse as such a
great primitive.
At this point I want to advertise my tryGet suggestion that returns an
Option again as I think it would satisfy the people wanting orElse without
the confusion orElse created in this discussion alone.
Also in this sense tryGet is the more pure form of the "primitive" as it
returns basically a tuple of the value and a boolean rather the value is
there. Which is pretty much the entire state the LazyConstant is carrying
without any transformation of information.
Great regards
RedIODev
On Tue, Dec 9, 2025, 11:25 Maurizio Cimadamore <
maurizio.cimadamore at oracle.com> wrote:
> I agree with most of the conclusions in this thread.
>
>
> One small nit is that, in reality, `orElse` is a "primitive" in disguise.
> E.g. you can implement `get` in terms of `orElse` but not the other way
> around (unless you are willing to do _two_ accessed to the underlying
> value). So, while we could drop it, we would also lose something (which is
> why we decided to keep it, at least for now).
>
>
> Maurizio
>
>
>
> On 08/12/2025 12:31, Per-Ake Minborg wrote:
>
> So, it is nice that folks seem to agree that LazyConstant should only
> compute and initialize its contents from the Supplier/lambda given at
> declaration time. The orElse method seems to blur the contours of
> LazyConstant , and so, as previously said, we might consider removing the
> method altogether in the next preview.
>
> It is also a fact that many have identified a need for "something else
> more low-level" that supports a more imperative programming model when
> working with constants that are lazily set. We do not rule out that such a
> thing might appear in a future JDK version.
>
> Best, Per
>
> Confidential- Oracle Internal
> ------------------------------
> *From:* David Alayachew <davidalayachew at gmail.com>
> <davidalayachew at gmail.com>
> *Sent:* Friday, December 5, 2025 2:51 PM
> *To:* Red IO <redio.development at gmail.com> <redio.development at gmail.com>
> *Cc:* david Grajales <david.1993grajales at gmail.com>
> <david.1993grajales at gmail.com>; Per-Ake Minborg
> <per-ake.minborg at oracle.com> <per-ake.minborg at oracle.com>; amber-dev
> <amber-dev at openjdk.org> <amber-dev at openjdk.org>; core-libs-dev
> <core-libs-dev at openjdk.org> <core-libs-dev at openjdk.org>
> *Subject:* [External] : Re: Feedback about LazyConstants API (JEP526)
>
> Caveat -- I have only used the Java 25 version of this library.
>
> I agree that the name orElse() is not intuitive. It was made more
> intuitive by the existence of orElseSet(). In its absence, changing the
> name makes sense.
>
> Though, I'm definitely open to just removing the method. This is easy
> enough to accomplish ourselves. Would prefer a rename though.
>
> On Fri, Dec 5, 2025, 8:32 AM Red IO <redio.development at gmail.com> wrote:
>
> Hi David,
> As par already said the orElse method doesn't initializes the
> LazyConstant.
> It just checks rather the value is init and if not calls the supplier to
> get a substitute for the missing constant.
> Example:
> LazyConstant<String> x = LazyConstant.of(() -> "Const");
> var uninit1 = x.orElse(() -> "substitute 1");
> var uninit2 = x.orElse(() -> "substitute 2");
> var init1 = x.get();
> var init2 = x.orElse(() -> "substitute 3");
> uninit1 and uninit2 get the substitute 1/2
> And init1 and init2 get Const.
>
> This is surprising if you expect it to be a way to init it with an
> alternative value.
>
> My suggestion would to make the separation clear and allow for another use
> case by spliting this api in 2 parts:
> One class LazyConstant
> Takes a Supplier in static factory and exposes get()
>
> And
> Class LazyInit
> Which takes no arguments in the static factory and takes a supplier in the
> get method that gets called when get is called for the first time.
> In this case the source for the constant can be any piece of code that has
> access to the LazyConstant. This might be desired in some cases. In cases
> where it's not the other version can be used.
>
> This split makes it clear from which context the constant is initialized
> from (consumer or at declaration)
>
> Mixing those 2 or having methods that appear to do this is rather
> confusing.
>
>
>
> One solution for the "i might not want to init the constant" case the
> "orElse" method is meant to be is to have a method "tryGet" which returns
> Optional instead. This makes it clear that the value might not be there and
> is not initialized when calling the method. Nobody expects to init the
> constant when calling orElse on a returned Optional.
>
> My 2 suggestions here are completely independent and should be viewed as
> such.
>
> Great regards
> RedIODev
>
> On Fri, Dec 5, 2025, 13:55 david Grajales <david.1993grajales at gmail.com>
> wrote:
>
> HI Per. I pleasure to talk with you.
>
> You are right about one thing but this actually makes the API less
> intuitive and harder to read and reason about.
>
> LazyConstant<String> foo = LazyConstant.of(() -> "hello");
>
> void main() {
> if (someCondition()) {// asume false
> foo.get();
> }
> foo.orElse("hello2"); // ...
>
> println(foo.get()); // This prints "hello"
> }
>
> But if one assigns foo.orElse("hello2") to a variable, the variable
> actually gets the "hello2" value.
>
> void main() {
> if (someCondition()) {// asume false
> foo.get();
> }
> var res = foo.orElse("hello2"); // ...
> var res2 = foo.orElse("hello3");
> println(res); // This prints "hello2"
> println(res2);//This prints "hello3"
> }
>
> This is actually even more confusing and makes the API more error prone. I
> personally think once initialized the lazy constant should always return
> the same value (maybe through the .get() method only), and there should not
> be any possibility of getting a different values from the same instance
> either in the .of() static method or in any hypothetical instance method
> for conditional downstream logic. I guess one could achieve the latter
> with the static factory method through something like this (although less
> elegant)
>
> private class Bar{
> private final LazyConstant<String> foo;
> private Bar(Some some){
>
> if(some.condition){
> foo = LazyConstant.of(() -> "hello");
> }else {
> foo = LazyConstant.of(() -> "hello2");
> }
> }
> }
>
> Thank you for reading. This is all I have to report.
>
> Best regards.
>
>
>
> El vie, 5 dic 2025 a la(s) 6:05 a.m., Per-Ake Minborg (
> per-ake.minborg at oracle.com) escribió:
>
> Hi David,
>
> Thank you for trying out LazyConstant and providing feedback. That is
> precisely what previews are for!
>
> If you take a closer look at the specification of LazyConstant::orElse, it
> says that the method will *never trigger initialization.* And so, you
> *can* actually be sure that in your first example, foo is always
> initialized to "hello" (if ever initialized). It is only if foo is not
> initialized that the method will return "hello2" (again, without
> initializing foo). This is similar to how Optional works.
>
> It would be possible to entirely remove the orElse() method from the API,
> and in the rare cases where an equivalent functionality is called for, rely
> on LazyConstant::isInitialized instead.
>
> Best, Per
>
>
> Confidential- Oracle Internal
> ------------------------------
> *From:* amber-dev <amber-dev-retn at openjdk.org> on behalf of david
> Grajales <david.1993grajales at gmail.com>
> *Sent:* Friday, December 5, 2025 5:38 AM
> *To:* amber-dev <amber-dev at openjdk.org>; core-libs-dev at openjdk.org <
> core-libs-dev at openjdk.org>
> *Subject:* Feedback about LazyConstants API (JEP526)
>
> Dear Java Dev Team,
>
> I am writing to provide feedback and two specific observations regarding
> the LazyConstant API, which is currently a preview feature in OpenJDK 26.
>
> I appreciate the API's direction and I think it's a good improvement
> compared to its first iteration; however, I see potential for improved
> expressiveness, particularly in conditional scenarios.
>
>
> *1. Proposal: Zero-Parameter `LazyConstant.of()` Overload:*
>
> Currently, the mandatory use of a factory method receiving a `Supplier`
> (due to the lack of a public constructor) can obscure the expressiveness of
> conditional or multiple-value initialization paths. **The Issue:** When
> looking at the declaration:
>
> LazyConstant<String> foo = LazyConstant.of(() -> "hello");
>
> the code gives the strong, immediate impression that the value is *always*
> initialized to "hello". This makes it difficult to infer that the
> constant might ultimately resolve to an alternative value set later via
> orElse() or another conditional path, especially when skimming the code:
>
> LazyConstant<String> foo = LazyConstant.of(() -> "hello"); // When
> skimming the code it's not always obvious that this may not be the actual
> value
>
> void main() {
> if (someCondition()) {
> foo.get(); // Trigger initialization to "hello"
> }
> // If someCondition is false, the final value of foo is determined here:
>
> var res1 = foo.orElse("hello2"); // ...
> }
>
> *My Suggestion:* I propose introducing a *zero-parameter overloaded
> static factory method* of():
>
> LazyConstant<String> foo = LazyConstant.of();
>
> This form explicitly communicates that the constant is initialized to an *
> unresolved* state, suggesting that the value will be determined
> downstream by the first invocation of an initialization/computation method.
>
> LazyConstant<String> foo = LazyConstant.of(); // Clearly unresolved
> void main() {
> if (someCondition()) {
> foo.orElse("hello");
> }
> var res1 = foo.orElse("hello2"); // ...
> }
>
> This is specially useful for clarity when one has conditional
> initialization in places such as the constructor of a class. For example
>
> private class Bar{
> LazyConstant<String> foo = LazyConstant.of();
> private Bar(Some some){
> if(some.condition()){
> foo.orElse("foo");
> }
> foo.orElse("foo2");
> }
>
> String computeValue() {
> return "hello";
> }
>
> String computeValue2(){
> return "hello2";
> }
> }
> 2. Method Naming Suggestion and and supplier in instance method for
> consistency in the API
>
> My second, much more minor observation relates to the instance method orElse(T
> t).
>
> While orElse fits a retrieval pattern, I personally feel that * compute*
> or *computeIfAbsent* would better express the intent of this method, as
> its primary function is not just to retrieve, but to trigger the
> computation and *set the final value* of the constant if it is currently
> uninitialized. Also, as the factory of() has a supplier i think this
> instance method should also receive a Supplier, This not only keeps the API
> consistent in the usage but makes more ergonomic the declaration of complex
> initialization logic inside the method.
>
>
> private class Bar{
> LazyConstant<InitParams> foo = LazyConstant.of(InitParam::default); //
> Under the current API this is mandatory but in reality the value is set in
> the constructor, default is never really used.
> private Bar(Some some){
> foo.compute(some::executeCallToCacheDBAndBringInitializationParams)
> //Real configuration happens here
>
> }
> }
>
> This last it's very common for initialization of configuration classes and
> singletons.
>
>
> Thank you so much for your attention, I hope you find this feedback useful.
>
> Always yours. David Grajales
>
>
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