New Collections interface - Sized

[Stephen Colebourne]

Hi all,
While a discussion on ReversibleCollection is going on, I'd like to
raise the interface I've always found most missing from the framework
- Sized

 public interface Sized {
   int size();
   default boolean isEmpty() {
     return size() == 0;
   }
   default boolean isNotEmpty() {
     return !isEmpty();
   }
}

This would be applied to Collection and Map, providing a missing
unification. Anything else that has a size could also be retrofitted,
such as String. Ideally arrays too, but that could come later. Note
that Iterable would not implement it.

WDYT?

Stephen