ImmutableSortedMap::copyOfSorted);
  }

  // unsafe, comparator() returns a comparator on the specified type
  @SuppressWarnings("unchecked")
  public static <K, V> ImmutableSortedMap<K, V> of() {
    return new Builder<K, V>((Comparator<K>) NATURAL_ORDER).build();
  }

  public static <K extends Comparable<? super K>, V> ImmutableSortedMap<K, V> of(K k1, V v1) {

          .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())

     */
    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);
  }

     */
    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);
  }

  // Creation tests

  public void testEmptyBuilder() {
    ImmutableSortedMap<String, Integer> map =
        ImmutableSortedMap.<String, Integer>naturalOrder().build();
    assertEquals(Collections.<String, Integer>emptyMap(), map);
  }

  public void testSingletonBuilder() {
    ImmutableSortedMap<String, Integer> map =
        ImmutableSortedMap.<String, Integer>naturalOrder().put("one", 1).build();

          .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())

 * 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
 */
public abstract class ImmutableMap<K, V> implements Map<K, V>, Serializable {

  abstract static class IteratorBasedImmutableMap<K, V> extends ImmutableMap<K, V> {

    assertEquals(ImmutableMap.of(), ArbitraryInstances.get(ImmutableMap.class));
    assertEquals(ImmutableSortedMap.of(), ArbitraryInstances.get(SortedMap.class));
    assertEquals(ImmutableSortedMap.of(), ArbitraryInstances.get(ImmutableSortedMap.class));
    assertEquals(ImmutableMultiset.of(), ArbitraryInstances.get(Multiset.class));

    assertEquals(ImmutableMap.of(), ArbitraryInstances.get(ImmutableMap.class));
    assertEquals(ImmutableSortedMap.of(), ArbitraryInstances.get(SortedMap.class));
    assertEquals(ImmutableSortedMap.of(), ArbitraryInstances.get(ImmutableSortedMap.class));
    assertEquals(ImmutableMultiset.of(), ArbitraryInstances.get(Multiset.class));

    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();
    }