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 <[email protected]>
<mailto:[email protected]>
*Sent:* Friday, December 5, 2025 2:51 PM
*To:* Red IO <[email protected]>
<mailto:[email protected]>
*Cc:* david Grajales <[email protected]>
<mailto:[email protected]>; Per-Ake Minborg
<[email protected]>
<mailto:[email protected]>; amber-dev
<[email protected]> <mailto:[email protected]>;
core-libs-dev <[email protected]>
<mailto:[email protected]>
*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
<[email protected]> 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
<[email protected]> 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
([email protected]) 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 <[email protected]> on
behalf of david Grajales <[email protected]>
*Sent:* Friday, December 5, 2025 5:38 AM
*To:* amber-dev <[email protected]>;
[email protected] <[email protected]>
*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
