@ElementTypesAreNonnullByDefault
public abstract class ImmutableSortedSet<E> extends ImmutableSet<E>
    implements NavigableSet<E>, SortedIterable<E> {
  /**
   * Returns a {@code Collector} that accumulates the input elements into a new {@code
   * ImmutableSortedSet}, ordered by the specified comparator.
   *
   * <p>If the elements contain duplicates (according to the comparator), only the first duplicate

  static final int SPLITERATOR_CHARACTERISTICS =
      ImmutableSet.SPLITERATOR_CHARACTERISTICS | Spliterator.SORTED;

  /**
   * Returns a {@code Collector} that accumulates the input elements into a new {@code
   * ImmutableSortedSet}, ordered by the specified comparator.
   *
   * <p>If the elements contain duplicates (according to the comparator), only the first duplicate

      Comparator<? super E> comparator, Iterator<? extends E> elements) {
    checkNotNull(comparator);
    return copyOfInternal(comparator, elements);
  }

  // We use NATURAL_ORDER only if the input was already using natural ordering.
  @SuppressWarnings("unchecked")
  public static <E> ImmutableSortedSet<E> copyOfSorted(SortedSet<E> sortedSet) {
    Comparator<? super E> comparator = sortedSet.comparator();