How to use

emptySortedSet

method

in

org.apache.sis.internal.util.CollectionsExt

/**
 * Returns an empty collection of the given type, or {@code null} if the given type is unknown to this method.
 *
 * @param  type  the desired collection type.
 * @return an empty collection of the given type, or {@code null} if the type is unknown.
 *
 * @since 0.8
 */
public static Collection<?> empty(final Class<?> type) {
  if (type.isAssignableFrom(List.class)) {                    // Most common case first.
    return Collections.EMPTY_LIST;
  } else if (type.isAssignableFrom(Set.class)) {
    return Collections.EMPTY_SET;
  } if (type.isAssignableFrom(SortedSet.class)) {
    return emptySortedSet();
  } else if (type.isAssignableFrom(Queue.class)) {
    return emptyQueue();
  } else {
    return null;
  }
}

if (SortedSet.class.isAssignableFrom(returnType)) {
  if (collection.isEmpty()) {
    collection = CollectionsExt.emptySortedSet();
  } else {
    collection = Collections.unmodifiableSortedSet(new TreeSet<>(collection));

if (type == List     .class) return (T) Collections.EMPTY_LIST;
if (type == Queue    .class) return (T) CollectionsExt.emptyQueue();
if (type == SortedSet.class) return (T) CollectionsExt.emptySortedSet();
if (type.isAssignableFrom(Set.class)) {
  return (T) Collections.EMPTY_SET;