*/
    return Collector.of(
        () -> new ImmutableSortedMap.Builder<K, V>(comparator),
        (builder, input) -> builder.put(keyFunction.apply(input), valueFunction.apply(input)),
        ImmutableSortedMap.Builder::combine,
        ImmutableSortedMap.Builder::buildOrThrow,
        Collector.Characteristics.UNORDERED);
  }

          .put(Map.class, ImmutableMap.of())
          .put(ImmutableMap.class, ImmutableMap.of())
          .put(SortedMap.class, ImmutableSortedMap.of())
          .put(ImmutableSortedMap.class, ImmutableSortedMap.of())
          .put(NavigableMap.class, Maps.unmodifiableNavigableMap(Maps.newTreeMap()))
          .put(Multimap.class, ImmutableMultimap.of())

          .put(Map.class, ImmutableMap.of())
          .put(ImmutableMap.class, ImmutableMap.of())
          .put(SortedMap.class, ImmutableSortedMap.of())
          .put(ImmutableSortedMap.class, ImmutableSortedMap.of())
          .put(NavigableMap.class, Maps.unmodifiableNavigableMap(Maps.newTreeMap()))
          .put(Multimap.class, ImmutableMultimap.of())

    if (ranges.isEmpty()) {
      return ImmutableMap.of();
    }
    RegularImmutableSortedSet<Range<K>> rangeSet =
        new RegularImmutableSortedSet<>(ranges, Range.<K>rangeLexOrdering());
    return new ImmutableSortedMap<>(rangeSet, values);
  }

  @Override
  public ImmutableMap<Range<K>, V> asDescendingMapOfRanges() {
    if (ranges.isEmpty()) {
      return ImmutableMap.of();
    }

    TreeMap<K, V> map = Maps.newTreeMap();
    map.put(key, value);
    return map;
  }

  @Generates
  static <K extends Comparable<? super K>, V> ImmutableSortedMap<K, V> generateImmutableSortedMap(
      K key, V value) {
    return ImmutableSortedMap.of(key, value);
  }

  @Generates
  static <K, V> Multimap<K, V> generateMultimap(@Nullable K key, @Nullable V value) {
    return generateListMultimap(key, value);

    if (ranges.isEmpty()) {
      return ImmutableMap.of();
    }
    RegularImmutableSortedSet<Range<K>> rangeSet =
        new RegularImmutableSortedSet<>(ranges, Range.<K>rangeLexOrdering());
    return new ImmutableSortedMap<>(rangeSet, values);
  }

  @Override
  public ImmutableMap<Range<K>, V> asDescendingMapOfRanges() {
    if (ranges.isEmpty()) {
      return ImmutableMap.of();
    }

    TreeMap<K, V> map = Maps.newTreeMap();
    map.put(key, value);
    return map;
  }

  @Generates
  static <K extends Comparable<? super K>, V> ImmutableSortedMap<K, V> generateImmutableSortedMap(
      K key, V value) {
    return ImmutableSortedMap.of(key, value);
  }

  @Generates
  static <K, V> Multimap<K, V> generateMultimap(@Nullable K key, @Nullable V value) {
    return generateListMultimap(key, value);

 * Collections#singletonMap(Object, Object)} and {@link java.util.LinkedHashMap} for empty,
 * singleton and regular maps respectively. For sorted maps, it's a thin wrapper around {@link
 * java.util.TreeMap}.
 *
 * @see ImmutableSortedMap
 * @author Hayward Chan
 */
@ElementTypesAreNonnullByDefault
public abstract class ImmutableMap<K, V> implements Map<K, V>, Serializable {

  // It is necessary here because otherwise the builder() method
  // would be inherited from the emulated ImmutableSet.
  // TODO(cpovirk): should we be including other methods from the shim here and
  // in ImmutableSortedMap?
  @Deprecated
  public static <E> ImmutableSortedSet.Builder<E> builder() {
    throw new UnsupportedOperationException();
  }

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

  }

  /**
   * Creates a <i>mutable</i>, empty {@code TreeMap} instance using the natural ordering of its
   * elements.
   *
   * <p><b>Note:</b> if mutability is not required, use {@link ImmutableSortedMap#of()} instead.
   *
   * <p><b>Note:</b> this method is now unnecessary and should be treated as deprecated. Instead,
   * use the {@code TreeMap} constructor directly, taking advantage of <a