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
