}

  static <E> Collector<E, ?, ImmutableSortedSet<E>> toImmutableSortedSet(
      Comparator<? super E> comparator) {
    checkNotNull(comparator);
    return Collector.of(
        () -> new ImmutableSortedSet.Builder<E>(comparator),
        ImmutableSortedSet.Builder::add,
        ImmutableSortedSet.Builder::combine,
        ImmutableSortedSet.Builder::build);
  }

                        mapEntry("a", (Collection<String>) ImmutableSortedSet.of("alex")),
                        mapEntry("b", (Collection<String>) ImmutableSortedSet.of("bob", "bagel")),
                        mapEntry("c", (Collection<String>) ImmutableSortedSet.of("carl", "carol")),
                        mapEntry("d", (Collection<String>) ImmutableSortedSet.of("david", "dead")),
                        mapEntry(

    assertTrue(multimap.get("a") instanceof ImmutableSortedSet);
    assertEquals(
        Collections.reverseOrder(), ((ImmutableSortedSet<Integer>) multimap.get("a")).comparator());
    assertTrue(multimap.get("x") instanceof ImmutableSortedSet);
    assertEquals(
        Collections.reverseOrder(), ((ImmutableSortedSet<Integer>) multimap.get("x")).comparator());

    assertThrows(ClassCastException.class, () -> ImmutableSortedSet.copyOf(original));
  }

  public void testImmutableSortedSetCopyOfIterator() {
    // false positive: `new Object()` is not equal to `new Object()`
    @SuppressWarnings("DistinctVarargsChecker")
    Set<Object> original = ImmutableSet.of(new Object(), new Object());

    assertThrows(ClassCastException.class, () -> ImmutableSortedSet.copyOf(original.iterator()));
  }

    assertTrue(multimap.get("a") instanceof ImmutableSortedSet);
    assertEquals(
        Collections.reverseOrder(), ((ImmutableSortedSet<Integer>) multimap.get("a")).comparator());
    assertTrue(multimap.get("x") instanceof ImmutableSortedSet);
    assertEquals(
        Collections.reverseOrder(), ((ImmutableSortedSet<Integer>) multimap.get("x")).comparator());

            .build();

    assertThat(RANGE_SET_ONE.difference(RANGE_SET_TWO)).isEqualTo(expected);
  }

  public void testAsSet() {
    ImmutableSortedSet<Integer> expectedSet = ImmutableSortedSet.of(2, 3, 4, 8, 9, 16, 17);
    ImmutableSortedSet<Integer> asSet = RANGE_SET_ONE.asSet(DiscreteDomain.integers());
    assertEquals(expectedSet, asSet);
    assertThat(asSet).containsExactlyElementsIn(expectedSet).inOrder();

            ContiguousSet.create(Range.open(0, 4), NOT_EQUAL_TO_INTEGERS),
            ImmutableSortedSet.of(1, 2, 3))
        .addEqualityGroup(
            ContiguousSet.create(Range.closedOpen(1, 1), integers()),
            ContiguousSet.closedOpen(1, 1),
            ContiguousSet.closedOpen(Integer.MIN_VALUE, Integer.MIN_VALUE),
            ImmutableSortedSet.of(),
            ImmutableSet.of())
        .testEquals();

    // path, so we test that separately
    assertTrue(range.containsAll(ImmutableSortedSet.of(3, 3, 4, 5)));
    assertTrue(range.containsAll(ImmutableSortedSet.of(3)));
    assertTrue(range.containsAll(ImmutableSortedSet.<Integer>of()));
    assertFalse(range.containsAll(ImmutableSortedSet.of(3, 3, 4, 5, 6)));

    assertTrue(Range.openClosed(3, 3).containsAll(Collections.<Integer>emptySet()));
  }

          .put(ImmutableList.class, ImmutableList.of())
          .put(Set.class, ImmutableSet.of())
          .put(ImmutableSet.class, ImmutableSet.of())
          .put(SortedSet.class, ImmutableSortedSet.of())
          .put(ImmutableSortedSet.class, ImmutableSortedSet.of())
          .put(NavigableSet.class, Sets.unmodifiableNavigableSet(Sets.newTreeSet()))
          .put(Map.class, ImmutableMap.of())
          .put(ImmutableMap.class, ImmutableMap.of())

    return (valueComparator == null)
        ? ImmutableSet.copyOf(values)
        : ImmutableSortedSet.copyOf(valueComparator, values);
  }

  private static <V> ImmutableSet<V> emptySet(@Nullable Comparator<? super V> valueComparator) {
    return (valueComparator == null)
        ? ImmutableSet.<V>of()
        : ImmutableSortedSet.<V>emptySet(valueComparator);
  }