*/
  public static <K extends @Nullable Object, V extends @Nullable Object> SortedMap<K, V> filterKeys(
      SortedMap<K, V> unfiltered, Predicate<? super K> keyPredicate) {
    // TODO(lowasser): Return a subclass of FilteredKeyMap for slightly better performance.
    return filterEntries(unfiltered, keyPredicateOnEntries(keyPredicate));
  }

  /**

   */
  public static <K extends @Nullable Object, V extends @Nullable Object> SortedMap<K, V> filterKeys(
      SortedMap<K, V> unfiltered, Predicate<? super K> keyPredicate) {
    // TODO(lowasser): Return a subclass of FilteredKeyMap for slightly better performance.
    return filterEntries(unfiltered, keyPredicateOnEntries(keyPredicate));
  }

  /**

  final Segment<K, V>[] newSegmentArray(int ssize) {
    return (Segment<K, V>[]) new Segment<?, ?>[ssize];
  }

  // Inner Classes

  /**
   * Segments are specialized versions of hash tables. This subclass inherits from ReentrantLock
   * opportunistically, just to simplify some locking and avoid separate construction.
   */
  @SuppressWarnings("serial") // This class is never serialized.