assertThat(multimap.get("bar")).containsExactly(6, 5).inOrder();
  }

  public void testSynchronizedSortedSetMultimap() {
    SortedSetMultimap<String, Integer> multimap =
        Multimaps.synchronizedSortedSetMultimap(TreeMultimap.<String, Integer>create());
    multimap.putAll("foo", Arrays.asList(3, -1, 2, 4, 1));
    multimap.putAll("bar", Arrays.asList(1, 2, 3, 1));

    assertThat(multimap.get("bar")).containsExactly(6, 5).inOrder();
  }

  public void testSynchronizedSortedSetMultimap() {
    SortedSetMultimap<String, Integer> multimap =
        Multimaps.synchronizedSortedSetMultimap(TreeMultimap.<String, Integer>create());
    multimap.putAll("foo", Arrays.asList(3, -1, 2, 4, 1));
    multimap.putAll("bar", Arrays.asList(1, 2, 3, 1));

          SortedSetMultimap<K, V> multimap, @CheckForNull Object mutex) {
    if (multimap instanceof SynchronizedSortedSetMultimap) {
      return multimap;
    }
    return new SynchronizedSortedSetMultimap<>(multimap, mutex);
  }

  static final class SynchronizedSortedSetMultimap<
          K extends @Nullable Object, V extends @Nullable Object>

 * read operations will work correctly. To allow concurrent update operations, wrap your multimap
 * with a call to {@link Multimaps#synchronizedSortedSetMultimap}.
 *
 * <p>See the Guava User Guide article on <a href=
 * "https://github.com/google/guava/wiki/NewCollectionTypesExplained#multimap">{@code Multimap}</a>.
 *
 * @author Jared Levy
 * @author Louis Wasserman

    TreeMultimap<String, Integer> delegate =
        TreeMultimap.create(Ordering.<String>natural(), INT_COMPARATOR);
    SortedSetMultimap<String, Integer> multimap = Multimaps.synchronizedSortedSetMultimap(delegate);
    checkUnmodifiableMultimap(multimap, false, "null", 42);
    assertSame(INT_COMPARATOR, multimap.valueComparator());
  }

  @J2ktIncompatible
  @GwtIncompatible // SerializableTester

    TreeMultimap<String, Integer> delegate =
        TreeMultimap.create(Ordering.<String>natural(), INT_COMPARATOR);
    SortedSetMultimap<String, Integer> multimap = Multimaps.synchronizedSortedSetMultimap(delegate);
    checkUnmodifiableMultimap(multimap, false, "null", 42);
    assertSame(INT_COMPARATOR, multimap.valueComparator());
  }

  @J2ktIncompatible
  @GwtIncompatible // SerializableTester

   * {@code map} and the instances generated by {@code factory} are. Concurrent read operations will
   * work correctly. To allow concurrent update operations, wrap the multimap with a call to {@link
   * #synchronizedSortedSetMultimap}.
   *
   * <p>Call this method only when the simpler methods {@link TreeMultimap#create()} and {@link
   * TreeMultimap#create(Comparator, Comparator)} won't suffice.
   *