Updated State of the Specialization

Brian Goetz brian.goetz at oracle.com
Sun Dec 21 16:07:28 UTC 2014

Value types need to have some form of at least some of the core Object 
methods, at least hashCode, equals, and toString.  Open questions here 

  - Will there be some interface that specifies these?  (C# has a root 
interfaces like this that all structs implement)
  - Will Object implement that interface?  (Seems nice for generic code, 
but then it can't be called anything Value-ish, would have to be called 
Object-ish, like "Objectionable" or "Objectifiable" or 

The compiler or VM would certainly generate default implementations of 
equals/hashCode that delegates to the components.  A further open 
question is whether these could be overridden by value types, or whether 
this is just part of their definition.  (And, if equals/hashCode are 
effectively final, its a little weird for toString to be standing alone, 
though would be permissible.)

On 12/21/2014 10:54 AM, Gustav Åkesson wrote:
> Hi,
> I'm going through the nitty-gritty details of this super exciting
> proposal, but one question came to mind which I couldn't find an
> explanation for in the proposal. If we have...
> class Summerizer<any T> {
>       int sumHashCodes(T ... entries) {
>         // Sum hash code values for all entries using ::hashCode()
>      }
> }
> ...then how will the specialized class for Summerizer<int> know that the
> same semantics as Integer::hashCode() should be inferred here? Same goes
> for the other primitive types.
> I'm thinking of e.g. equals as well. Using synchronized on the type
> could be prohibited (as stated by the Language restriction section), but
> what above methods inherited from Object?
> Best Regards,
> Gustav Åkesson
> On Fri, Dec 19, 2014 at 10:31 PM, Brian Goetz <brian.goetz at oracle.com
> <mailto:brian.goetz at oracle.com>> wrote:
>     I've updated the State of the Specialization here:
>     http://cr.openjdk.java.net/~__briangoetz/valhalla/__specialization.html
>     <http://cr.openjdk.java.net/~briangoetz/valhalla/specialization.html>
>     The old version is here:
>     http://cr.openjdk.java.net/~__briangoetz/valhalla/__specialization-1.html
>     <http://cr.openjdk.java.net/~briangoetz/valhalla/specialization-1.html>

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