Map<? extends K, ? extends V> map, Comparator<? super K> comparator) {
    boolean sameComparator = false;
    if (map instanceof SortedMap) {
      SortedMap<?, ?> sortedMap = (SortedMap<?, ?>) map;
      Comparator<?> comparator2 = sortedMap.comparator();
      sameComparator =
          (comparator2 == null) ? comparator == NATURAL_ORDER : comparator.equals(comparator2);
    }

      SortedMap<K, V> sortedMap, @CheckForNull Object mutex) {
    return new SynchronizedSortedMap<>(sortedMap, mutex);
  }

  static class SynchronizedSortedMap<K extends @Nullable Object, V extends @Nullable Object>
      extends SynchronizedMap<K, V> implements SortedMap<K, V> {

    SynchronizedSortedMap(SortedMap<K, V> delegate, @CheckForNull Object mutex) {

  private static <K, V> SortedMap<K, V> sortedNotNavigable(final SortedMap<K, V> map) {
    return new ForwardingSortedMap<K, V>() {
      @Override
      protected SortedMap<K, V> delegate() {
        return map;
      }
    };
  }

  public void testSortedMapTransformValues() {
    SortedMap<String, Integer> map = sortedNotNavigable(ImmutableSortedMap.of("a", 4, "b", 9));

  private static <K, V> SortedMap<K, V> sortedNotNavigable(final SortedMap<K, V> map) {
    return new ForwardingSortedMap<K, V>() {
      @Override
      protected SortedMap<K, V> delegate() {
        return map;
      }
    };
  }

  public void testSortedMapTransformValues() {
    SortedMap<String, Integer> map = sortedNotNavigable(ImmutableSortedMap.of("a", 4, "b", 9));

      Map<? extends K, ? extends V> map, Comparator<? super K> comparator) {
    boolean sameComparator = false;
    if (map instanceof SortedMap) {
      SortedMap<?, ?> sortedMap = (SortedMap<?, ?>) map;
      Comparator<?> comparator2 = sortedMap.comparator();
      sameComparator =
          (comparator2 == null) ? comparator == NATURAL_ORDER : comparator.equals(comparator2);
    }

     * @param m
     *            作成されるマップに配置されるマップ
     * @return {@link ConcurrentSkipListMap}の新しいインスタンス
     * @see ConcurrentSkipListMap#ConcurrentSkipListMap(SortedMap)
     */
    public static <K, V> ConcurrentSkipListMap<K, V> newConcurrentSkipListMap(final SortedMap<K, ? extends V> m) {
        return new ConcurrentSkipListMap<>(m);
    }

    /**
     * {@link ConcurrentSkipListSet}の新しいインスタンスを作成して返します。
     *