Helper classes

[Paul Benedict]

Zhong, but at least you can prevent instantiating a class with "final" or
throwing AssertionError in a private constructor. If you create an
interface with all static methods, you will still have an interface that
someone can extend or implement.

Paul


On Mon, Apr 15, 2013 at 5:01 PM, Zhong Yu <zhong.j.yu at gmail.com> wrote:

> Also there's another design possibility: a vacuous interface,
> containing no abstract methods, but all default methods, for example
>
>     public interface Math
>         int max(int, int)
>
> as contrast to the traditional way: a vacuous class, not a template
> for objects, but only as a namespace hosting static methods.
>
> Zhong Yu
>
>
> On Mon, Apr 15, 2013 at 4:23 PM, Sam Pullara <spullara at gmail.com> wrote:
> > I don't feel like we would be having this discussion if Java always
> > had statics in interfaces. It is the obvious place to put helpers that
> > are factories and other cases that do not act directly on the
> > interface type. So much so that people often put an inner class in the
> > interface just to get some semblance of this behavior.
> >
> > Sam
> >
> > On Apr 15, 2013, at 1:59 PM, Luc Duponcheel <luc.duponcheel at gmail.com>
> wrote:
> >
> >> Hello,
> >>
> >> Here is my opinion on this:
> >>
> >> Functionality naturally belongs to interface, say Zyx, if one of it's
> >> parameters is of type Zyx
> >> (and if an argument passed to it is, naturally, eagerly evaluated).
> >>
> >> Other functionality naturally belongs to helper class. say Zyxs (or
> >> ZyxStatics for that matter).
> >>
> >> for example:
> >>
> >> - transforming an element to a singleton list containing it naturally
> >> belongs to the helper class
> >> - joining a list of lists naturally belongs to the helper class
> >>
> >> On the other hand it is sometimes useful to have static versions of
> methods
> >> in Zyx in Zyxs because they can naturally be used as method references.
> >>
> >> About discoverability:
> >>
> >> When, for example, working with lists, I hope that there will be zipper
> >> functionaity transforming a tuple of lists into a list of tuples. That
> >> functionality naturally fits in the interface Zyx (maybe with a copy in
> the
> >> class Zyxs). I also hope that there will be unzipper functionality
> >> transforming a list of tuples into a tuple of lists. That functionality
> >> naturally fits in the class Zyxs. So, if you know what method you are
> >> looking for (also in terms of its signature) you often know where to
> look
> >> it for.
> >>
> >> By the way:
> >> my experimental JavaZ library (https://github.com/JavaZ) contains many
> >> examples:
> >>
> >> e.g. bindF (a.k.a. map) in Zyx has a version liftF in ZyxStatics (its
> >> method reference is used in foreach)
> >>
> >> Luc
> >>
> >> --
> >>   __~O
> >>  -\ <,
> >> (*)/ (*)
> >>
> >> reality goes far beyond imagination
> >>
> >
>
>