* href="https://github.com/google/guava/wiki/UsingAndAvoidingNullExplained#optional">using {@code
 * Optional}</a>.
 *
 * @param <T> the type of instance that can be contained. {@code Optional} is naturally covariant on
 *     this type, so it is safe to cast an {@code Optional<T>} to {@code Optional<S>} for any
 *     supertype {@code S} of {@code T}.
 * @author Kurt Alfred Kluever
 * @author Kevin Bourrillion
 * @since 10.0

       *   failure during the initial lookup of the path argument itself is rethrown directly. So
       *   any exception that we're seeing here is from a descendant, which naturally has a parent.
       *   I think.
       *
       * Still, if this can happen somehow (a weird filesystem implementation that lets callers

       *   failure during the initial lookup of the path argument itself is rethrown directly. So
       *   any exception that we're seeing here is from a descendant, which naturally has a parent.
       *   I think.
       *
       * Still, if this can happen somehow (a weird filesystem implementation that lets callers

   * element is found, {@code defaultValue} will be returned from this method and the iterator will
   * be left exhausted: its {@code hasNext()} method will return {@code false}. Note that this can
   * usually be handled more naturally using {@code tryFind(iterator, predicate).or(defaultValue)}.
   *
   * @since 7.0
   */
  // For discussion of this signature, see the corresponding overload of *Iterables*.find.
  @CheckForNull

  private static final Comparator<?> NATURAL_ORDER = Ordering.natural();

  private static final ImmutableSortedMap<Comparable<?>, Object> NATURAL_EMPTY_MAP =
      new ImmutableSortedMap<>(
          ImmutableSortedSet.emptySet(Ordering.natural()), ImmutableList.<Object>of());

  static <K, V> ImmutableSortedMap<K, V> emptyMap(Comparator<? super K> comparator) {
    if (Ordering.natural().equals(comparator)) {
      return of();
    } else {

        .addEqualityGroup(Ordering.natural())
        .testEquals();
  }

  public void testIsInOrder() {
    assertFalse(isInOrder(asList(5, 3, 0, 9), Ordering.natural()));
    assertFalse(isInOrder(asList(0, 5, 3, 9), Ordering.natural()));
    assertTrue(isInOrder(asList(0, 3, 5, 9), Ordering.natural()));
    assertTrue(isInOrder(asList(0, 0, 3, 3), Ordering.natural()));

 *
 * @author Chris Povirk
 * @author Jared Levy
 */
@GwtCompatible
@ElementTypesAreNonnullByDefault
public abstract class TestIntegerSortedSetGenerator extends TestIntegerSetGenerator {
  @Override
  protected abstract SortedSet<Integer> create(Integer[] elements);

  /** Sorts the elements by their natural ordering. */
  @Override

    assertEquals(tree, copyFromTree);
    assertSame(Ordering.natural(), copyFromTree.keyComparator());
    assertSame(Ordering.natural(), copyFromTree.valueComparator());
    assertSame(Ordering.natural(), copyFromTree.get(1.0).comparator());
  }

  /** Test that creating one TreeMultimap from a non-TreeMultimap results in natural ordering. */
  public void testCreateFromHashMultimap() {

 *       directly
 *   <li>Pass a <i>pre-existing</i> {@link Comparator} instance to {@link #from(Comparator)}
 *   <li>Use the natural ordering, {@link Ordering#natural}
 * </ul>
 *
 * <h4>Chaining</h4>
 *
 * <p>Then you can use the <i>chaining</i> methods to get an altered version of that {@code
 * Ordering}, including:
 *
 * <ul>
 *   <li>{@link #reverse}

    ImmutableTable.Builder<Character, Integer, String> builder = ImmutableTable.builder();
    Table<Character, Integer, String> copy =
        builder
            .orderRowsBy(Ordering.natural())
            .orderColumnsBy(Ordering.natural())
            .putAll(table)
            .build();
    assertThat(copy.rowKeySet()).containsExactly('a', 'b').inOrder();
    assertThat(copy.columnKeySet()).containsExactly(1, 2).inOrder();