Most recent JEP 401 description

[John Bossons]

Thanks for the confirmation. Good news!

As to 'no restrictions' re size (horizontal - number of fields), fine. But
what about depth (vertical - fields that are value objects that in turn
contain fields that are value objects etc. all the way down)? No constraint
on depth of nesting?





On Sat, May 18, 2024 at 8:21 PM Brian Goetz <brian.goetz at oracle.com> wrote:

> Amazingly, yes, value-capable abstract classes can have fields.  We
> thought for many years this would never be possible; the Great
> Initialization Alignment (eliminating `vnew` and `withfield` in favor of
> the `new` and `putfield` approach) made this possible.
>
> The language imposes no restrictions on the number of fields of value
> types.  The VM reserves the right to flatten, or not, based on its whims.
> One likely whim is that "large" values are usually not worth flattening.
> But this is invisible to the user; the semantics are the same whether or
> not the object is flattened.
>
> On 5/18/2024 1:24 PM, John Bossons wrote:
>
> Thanks for making this so very clear.
>
> Two questions/issues:
> (1) It would be helpful to include more on the properties of abstract
> value classes (AVCs) -- perhaps a labelled subsection? A specific question
> not dealt with explicitly in the current version: Can an AVC have an
> instance field, now that a value class utilizes the Flexible Constructor
> Bodies JEP? (The alternative is  repetition of that field definition and
> accessor in every subtype, which is potentially error-prone).
> (2) It would also be helpful to include some commentary on limitations.
> Specifically, although it is clear that the purpose is more efficiently
> defined SMALL value objects, (a) How big is 'small'? And (b) will the
> compiler accept value types of any size, no matter how deep?
>
> John
>
>
> Phone:  (416) 450-3584 (cell)
>
>
>

-- 
Phone:  (416) 450-3584 (cell)
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