public SafeTreeMap() {
    this(new TreeMap<K, V>());
  }

  public SafeTreeMap(Comparator<? super K> comparator) {
    this(new TreeMap<K, V>(comparator));
  }

  public SafeTreeMap(Map<? extends K, ? extends V> map) {
    this(new TreeMap<K, V>(map));
  }

  public SafeTreeMap(SortedMap<K, ? extends V> map) {
    this(new TreeMap<K, V>(map));
  }

 * that are equal to each other but unequal to the objects in any other group. For example:
 *
 * <pre>
 * new EqualsTester()
 *     .addEqualityGroup(new User("page"), new User("page"))
 *     .addEqualityGroup(new User("sergey"))
 *     .testEquals();
 * </pre>
 *
 * <p>This tests:
 *
 * <ul>
 *   <li>comparing each object against itself returns true

    @Test
    void testHashCodeNullSafe() {
        new ActivationProperty().hashCode();
    }

    @Test
    void testEqualsNullSafe() {
        assertFalse(new ActivationProperty().equals(null));

        new ActivationProperty().equals(new ActivationProperty());
    }

    @Test
    void testEqualsIdentity() {
        ActivationProperty thing = new ActivationProperty();

class DeveloperTest {

    @Test
    void testHashCodeNullSafe() {
        new Developer().hashCode();
    }

    @Test
    void testEqualsNullSafe() {
        assertFalse(new Developer().equals(null));

        new Developer().equals(new Developer());
    }

    @Test
    void testEqualsIdentity() {
        Developer thing = new Developer();

 *
 */
class ParentTest {

    @Test
    void testHashCodeNullSafe() {
        new Parent().hashCode();
    }

    @Test
    void testEqualsNullSafe() {
        assertFalse(new Parent().equals(null));

        new Parent().equals(new Parent());
    }

    @Test
    void testEqualsIdentity() {
        Parent thing = new Parent();
        assertTrue(thing.equals(thing), "Expected " + thing + " to equal " + thing);

    @Test
    void testHashCodeNullSafe() {
        new Prerequisites().hashCode();
    }

    @Test
    void testEqualsNullSafe() {
        assertFalse(new Prerequisites().equals(null));

        new Prerequisites().equals(new Prerequisites());
    }

    @Test
    void testEqualsIdentity() {
        Prerequisites thing = new Prerequisites();

 *
 */
class SiteTest {

    @Test
    void testHashCodeNullSafe() {
        new Site().hashCode();
    }

    @Test
    void testEqualsNullSafe() {
        assertFalse(new Site().equals(null));

        new Site().equals(new Site());
    }

    @Test
    void testEqualsIdentity() {
        Site thing = new Site();
        assertTrue(thing.equals(thing), "Expected " + thing + " to equal " + thing);
    }

   */
  public static <E> Builder<E> orderedBy(Comparator<E> comparator) {
    return new Builder<>(comparator);
  }

  /**
   * Returns a builder that creates immutable sorted sets whose elements are ordered by the reverse
   * of their natural ordering.
   */
  public static <E extends Comparable<?>> Builder<E> reverseOrder() {
    return new Builder<>(Collections.reverseOrder());
  }

  /**

  transient Class<K> keyTypeOrObjectUnderJ2cl;

  /**
   * Returns a new, empty {@code EnumHashBiMap} using the specified key type.
   *
   * @param keyType the key type
   */
  public static <K extends Enum<K>, V extends @Nullable Object> EnumHashBiMap<K, V> create(
      Class<K> keyType) {
    return new EnumHashBiMap<>(keyType);
  }

  /**
   * Constructs a new bimap with the same mappings as the specified map. If the specified map is an

    return (Collector) TO_OPTIONAL;
  }

  private static final Object NULL_PLACEHOLDER = new Object();

  private static final Collector<@Nullable Object, ?, @Nullable Object> ONLY_ELEMENT =
      Collector.<@Nullable Object, ToOptionalState<Object>, @Nullable Object>of(
          () -> new ToOptionalState<>(null),
          (state, o) -> state.add((o == null) ? NULL_PLACEHOLDER : o),
          ToOptionalState::combine,