String name();
  }

  public interface InternerImplEnum {
    <E> Interner<E> create(Collection<E> contents);

    String name();
  }

  public enum SetImpl implements CollectionsImplEnum {
    HashSetImpl {
      @Override
      public <E extends Comparable<E>> Set<E> create(Collection<E> contents) {
        return new HashSet<E>(contents);
      }
    },
    LinkedHashSetImpl {
      @Override