Another way to think about this is:
1. First, default methods are not inherently bad. They are useful in many
situations and can be "overridden" on implementing classes, if necessary.
2. A default method should be provided when the operation is not strictly
required or if the implementation (procedure/algorithm) is rather simple
(e.g. following the template pattern), for example...
@FunctionalInterace {
interface Sorter {
default Object[] sort(Object... array) {
return convert(Arrays.asList(array)).toArray();
}
<T extends Iterable<?>> T convert(T collection);
}
3. If the interface footprint is small (as it should be) then it is
possible to use in *Lambda* expressions (and *Method References*), as
proper @FunctionalInterface as shown above, which is very useful when
composing *Streams*, etc.
Food for thought.
-j
On Fri, May 8, 2020 at 10:17 AM Jacob Barrett <jbarr...@pivotal.io> wrote:
> As a general rule default implementations on an interface should only used
> when absolutely necessary because all the implementations are out of your
> control. For example, the collection interfaces in the JDK all gained new
> APIs but Java doesn’t implement every instance of them so a default is
> necessary for forward progress. However, if you own all instances you
> should not need to use default. So in this particular PR the use of default
> in the InternalCache in my opinion is wrong. We should control all internal
> interfaces and therefor can update them all with the correct
> implementation.
>
> -Jake
>
> > On May 8, 2020, at 9:49 AM, Kirk Lund <kl...@apache.org> wrote:
> >
> > I believe some of the Geode community has already decided that we
> shouldn't
> > overuse default methods in interfaces. Dan and others were the ones who
> > decided this and thus I can't really explain to folks in PRs why it's bad
> > to overuse default methods. Could some of the folks with strong
> > understanding of why we should avoid making every method default empty
> > please speak up here and/or in https://github.com/apache/geode/pull/5014
> ?
> >
> > My understanding is that default implementations should only be provided
> in
> > interfaces when it's important to do so for facilitating some sort of
> > deprecation and replacing a deprecated method.
> >
> > Thanks,
> > Kirk
>
>
--
-John
Spring Data Team
