Enumeration adapters in SE 8

Ben Evans benjamin.john.evans at gmail.com
Wed Aug 24 14:45:03 PDT 2011

Hi Dan,

On Wed, Aug 24, 2011 at 7:10 PM, Dan Smith <daniel.smith at oracle.com> wrote:

> I was pointed to some comments on core-libs about adapting Enumerations to
> for loops in SE 8.  (Sorry for the new thread -- I wasn't subscribed.)  It
> turns out lambdas + extension methods will make this very easy.
> In the API:
> interface Enumeration<E> extends Iterator<E> {
>  boolean hasMoreElements();
>  E nextElement();
>  boolean hasNext() default #hasMoreElements;
>  E next() default #nextElement;
>  void remove() default { throw new UnsupportedOperationException(); }
> }
> Note that Iterable is a function type -- a thunk producing an Iterator --
> and so we can express Iterables with lambdas and method references.  It's
> becoming clear that a for loop should provide a target type for these
> things, so that will probably be part of the SE 8 feature set.
> With a method reference:
> Hashtable<String,Object> h = …;
> for (String s : h#keys) { … }

I'm struggling to see where this might be useful. This example is obviously
too trivial and would add nothing, but I can't see to come up with any more
extensive example where having a method reference in this position would be
actually useful.

Can someone else provide a more compelling example for a for loop taking a
method reference?



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