* backing collection and the mutex are serializable.
 *
 * <p>If {@code null} is passed as the {@code mutex} parameter to any of this class's top-level
 * methods or inner class constructors, the created object uses itself as the synchronization mutex.
 *
 * <p>This class should be used by other collection classes only.
 *
 * @author Mike Bostock

 * com.google.common.net.InternetDomainName}.</b>
 *
 * <p>A generated static class containing public members which provide domain name patterns used in
 * determining whether a given domain name is an effective top-level domain (public suffix).
 *
 * <p>Because this class is used in GWT, the data members are stored in a space-efficient manner.
 * See {@link TrieParser}.
 *
 * @since 16.0
 */
@GwtCompatible
@Beta

    public MergingIterator(
        Iterable<? extends Iterator<? extends T>> iterators, Comparator<? super T> itemComparator) {
      // A comparator that's used by the heap, allowing the heap
      // to be sorted based on the top of each iterator.
      Comparator<PeekingIterator<T>> heapComparator =
          (PeekingIterator<T> o1, PeekingIterator<T> o2) ->
              itemComparator.compare(o1.peek(), o2.peek());