* iterating over it or any of its {@code descendingSet}, {@code subSet}, {@code headSet}, or
   * {@code tailSet} views.
   *
   * {@snippet :
   * NavigableSet<E> set = synchronizedNavigableSet(new TreeSet<E>());
   *  ...
   * synchronized (set) {
   *   // Must be in the synchronized block
   *   Iterator<E> it = set.iterator();
   *   while (it.hasNext()) {
   *     foo(it.next());