Value types and parameter names

Brian Goetz brian.goetz at
Mon Dec 1 19:18:15 UTC 2014

This is two separate questions, with one answer:

Q:  Would parameter names be available for value types?
A:  I see no reason why the answer for this should be any different than 
for reference classes.

Q:  Could it be turned on by default?
A:  I see no reason why the answer for this should be any different than 
for reference classes.

In both cases, there's nothing special about value types that should 
interact with parameter names in any non-obvious way; doing otherwise 
would just introduce needless complexity.  Value types are defined by 
classes just as reference types are, can have methods just like 
reference types do, and the treatment of parameter names in methods of 
value types should be identical to those of reference types.

Now, maybe what you really are getting at is that you're asking to 
revisit the "why were they not turned on by default" decision (which was 
a complex decision that involved balancing multiple considerations)?

On 12/1/2014 2:02 PM, Lovro Pandzic wrote:
> Hello all,
> I've been monitoring the Valhalla project for some time now and I have a
> question: will the new parameter names API introduced in Java 8 be
> available for value types? If so, is there a possibility for it to be
> turned on by default?
> One great thing I like about the new parameter names is that it provides a
> supported way for eliminating the need of JavaBeans setters. See [1] for
> example. In various libraries and frameworks, setters are often used as a
> tool for both discovering component names of an object and for injecting
> those components while constructing it because parameter names of
> constructors were not available through reflection, at least not until Java
> 8. This approach goes against simplicity, immutability and only presents
> boilerplate in the code. Luckily, value types are planned to be immutable
> so setters are impossible.
> On the other hand, without setters, the only way for constructing those
> value types in those frameworks would be to use those constructor if they
> have parameter names available at runtime.
> [1]
> Kind Regards,
> Lovro Pandzic

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