[Zhong Yu]

Is it not possible to add state to interface through default methods?

    interface WithFoo
        int getFoo() default {  return fooMap.get(this);  }
        void setFoo(int x) default { fooMap.set(this, x); }

    static WeakConcurrentMap fooMap = new ...;

Zhong Yu

On Mon, Dec 19, 2011 at 2:35 AM, Lukas Eder <lukas.eder at gmail.com> wrote:
>> I understand extension methods are vital for evolving interfaces.
>> But in my opinion they should be used for just that. If we start
>> adding "final" extension methods too, then why not simply
>> introduce multiple inheritance straightaway?
>
> According to page 42 of the presentation I mentioned, extension
> methods really *are* an additional means of multiple inheritance,
> "final" or not. Interfaces already provide multiple inheritance of
> types, now there'll also be multiple inheritance of "behaviour", or
> something similar to "stateless traits":
> http://blogs.oracle.com/briangoetz/resource/devoxx-lang-lib-vm-co-evol.pdf
>
> Whether "final" is allowed or not is probably not very important to
> that discussion.
>
> Regards,
> Lukas
>