new ImmutableSortedMap<>(ImmutableSortedSet.emptySet(Ordering.natural()), ImmutableList.of());

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

  /**

  public static <E extends Comparable<? super E>> ImmutableSortedMultiset<E> of(E e1) {
    RegularImmutableSortedSet<E> elementSet =
        (RegularImmutableSortedSet<E>) ImmutableSortedSet.of(e1);
    long[] cumulativeCounts = {0, 1};
    return new RegularImmutableSortedMultiset<>(elementSet, cumulativeCounts, 0, 1);
  }

  /**

        return ImmutableSet.copyOf(contents);
      }
    },
    ImmutableSortedSetImpl {
      @Override
      public <E extends Comparable<E>> Set<E> create(Collection<E> contents) {
        return ImmutableSortedSet.copyOf(contents);
      }
    },
    ContiguousSetImpl {
      @Override
      public <E extends Comparable<E>> Set<E> create(Collection<E> contents) {
        return ContiguousSet.copyOf(contents);

  public static <E extends Comparable<? super E>> ImmutableSortedMultiset<E> of(E e1) {
    RegularImmutableSortedSet<E> elementSet =
        (RegularImmutableSortedSet<E>) ImmutableSortedSet.of(e1);
    long[] cumulativeCounts = {0, 1};
    return new RegularImmutableSortedMultiset<>(elementSet, cumulativeCounts, 0, 1);
  }

  /**

   * order in which they appear in the input.
   *
   * <p>If your data has no duplicates, or you wish to deduplicate elements, use {@code
   * ImmutableSortedSet.copyOf(elements)}; if you want a {@code List} you can use its {@code
   * asList()} view.
   *
   * <p><b>Java 8+ users:</b> If you want to convert a {@link java.util.stream.Stream} to a sorted

  // TreeSet

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

import java.util.List;
import java.util.Set;
import junit.framework.TestCase;
import org.jspecify.annotations.NullMarked;
import org.jspecify.annotations.Nullable;

/**
 * Base class for {@link ImmutableSet} and {@link ImmutableSortedSet} tests.
 *
 * @author Kevin Bourrillion
 * @author Jared Levy
 */
@GwtCompatible
@NullMarked
public abstract class AbstractImmutableSetTest extends TestCase {

 *       how the collection was created. Typically this is insertion order unless an explicit
 *       ordering is otherwise specified (e.g. {@link ImmutableSortedSet#naturalOrder}). See the
 *       appropriate factory method for details. View collections such as {@link
 *       ImmutableMultiset#elementSet} iterate in the same order as the parent, except as noted.

        () -> map.headMap("r", false).tailMap("m", true).keySet().add("a"));
  }

  @GwtIncompatible // NavigableMap
  public void testAsMapNavigableEmpty() {
    NavigableSet<String> strings = ImmutableSortedSet.of();
    NavigableMap<String, Integer> map = Maps.asMap(strings, LENGTH_FUNCTION);
    assertThat(map.entrySet()).isEmpty();
    assertTrue(map.isEmpty());
    assertThat(map.get("five")).isNull();
  }

        () -> map.headMap("r", false).tailMap("m", true).keySet().add("a"));
  }

  @GwtIncompatible // NavigableMap
  public void testAsMapNavigableEmpty() {
    NavigableSet<String> strings = ImmutableSortedSet.of();
    NavigableMap<String, Integer> map = Maps.asMap(strings, LENGTH_FUNCTION);
    assertThat(map.entrySet()).isEmpty();
    assertTrue(map.isEmpty());
    assertThat(map.get("five")).isNull();
  }