`this` in concise method bodies

[Victor Nazarov]

пт, 12 окт. 2018 г., 20:16 Brian Goetz <brian.goetz at oracle.com>:

> On 10/5/2018 7:22 PM, Dan Smith wrote:
> > - It's not totally clear what we do with 'this'. Kind of seems like it
> > should be treated as the first parameter to be passed, but there are
> > also examples in the JEP that ignore it. And is it allowed to be
> > referenced by the receiver expression?
> >
> > void reverse() = Collections::reverse; // invoke
> > Collections.reverse(this)?
> > int length(String s) = String::length; // invoke s.length()?
> > void altMethod() = ThisClass::method; // invoke this.method()?
> > void altMethod2() = this::method; // legal?
>
> Drilling in on `this`:
>
> One of the strongest motivating examples was:
>
>      static final Comparator c = ...
>
>      int compareTo(T other) = c::compare;
>
> And in this case, we want this to wire to c.compare(this, other).
>
> However, another strong motivating case is:
>
>      final List myList = ...
>
>      int size() = myList::size;
>
> in which case we want this to wire to myList.size() and ignore `this`
> entirely.
>
> And, both use cases are equally desirable.
>

I still think that it is a good idea to disambiguate two cases with
this-argument syntax introduced in Java 8:

int compareTo(T this, T that) = comparator::compare;

int size() = myList::size;

Writing this-argument seems to be not too much hussle and I think it is
very clear and explicit way to specify delegation behaviour...

--
Victor Nazarov