() -> ImmutableBiMap.ofEntries((Entry<Integer, Integer>) nullKey));
    Entry<Integer, @Nullable Integer> nullValue =
        ImmutableBiMapTest.<@Nullable Integer>entry(23, null);
    assertThrows(
        NullPointerException.class,
        () -> ImmutableBiMap.ofEntries((Entry<Integer, Integer>) nullValue));
  }

  private static <T extends @Nullable Object> Entry<T, T> entry(T key, T value) {

import static org.hamcrest.CoreMatchers.equalTo;
import static org.hamcrest.CoreMatchers.is;
import static org.hamcrest.CoreMatchers.notNullValue;
import static org.hamcrest.CoreMatchers.nullValue;
import static org.hamcrest.MatcherAssert.assertThat;
import static org.hamcrest.collection.IsIterableContainingInAnyOrder.containsInAnyOrder;
import static org.junit.jupiter.api.Assertions.assertEquals;

      boolean permitsDuplicates,
      @Nullable String nullKey,
      @Nullable Integer nullValue) {
    multimap.clear();
    multimap.put("foo", 1);
    multimap.put("foo", 2);
    multimap.put("foo", 3);
    multimap.put("bar", 5);
    multimap.put("bar", -1);
    multimap.put(nullKey, nullValue);
    multimap.put("foo", nullValue);
    multimap.put(nullKey, 5);
    multimap.put("foo", 2);

        () -> ImmutableMap.ofEntries((Entry<Integer, Integer>) nullKey));
    Entry<@Nullable Integer, @Nullable Integer> nullValue = entry(23, null);
    assertThrows(
        NullPointerException.class,
        () -> ImmutableMap.ofEntries((Entry<Integer, Integer>) nullValue));
  }

  private static <T> Map<T, T> map(T... keysAndValues) {
    assertThat(keysAndValues.length % 2).isEqualTo(0);

        () -> ImmutableMap.ofEntries((Entry<Integer, Integer>) nullKey));
    Entry<@Nullable Integer, @Nullable Integer> nullValue = entry(23, null);
    assertThrows(
        NullPointerException.class,
        () -> ImmutableMap.ofEntries((Entry<Integer, Integer>) nullValue));
  }

  private static <T> Map<T, T> map(T... keysAndValues) {
    assertThat(keysAndValues.length % 2).isEqualTo(0);

    assertNull(segment.get(new Object(), hash));

    // null key
    DummyEntry<Object, Object> nullEntry = DummyEntry.create(null, hash, entry);
    Object nullValue = new Object();
    ValueReference<Object, Object> nullValueRef = map.newValueReference(nullEntry, nullValue, 1);
    nullEntry.setValueReference(nullValueRef);
    table.set(index, nullEntry);
    // skip the null key
    assertSame(value, segment.get(key, hash));

    assertNull(segment.get(new Object(), hash));

    // null key
    DummyEntry<Object, Object> nullEntry = DummyEntry.create(null, hash, entry);
    Object nullValue = new Object();
    ValueReference<Object, Object> nullValueRef = map.newValueReference(nullEntry, nullValue, 1);
    nullEntry.setValueReference(nullValueRef);
    table.set(index, nullEntry);
    // skip the null key
    assertSame(value, segment.get(key, hash));

    boolean nullKeys = inverseFeatures.remove(MapFeature.ALLOWS_NULL_KEYS);
    boolean nullValues = inverseFeatures.remove(MapFeature.ALLOWS_NULL_VALUES);

    if (nullKeys) {
      inverseFeatures.add(MapFeature.ALLOWS_NULL_VALUES);
    }
    if (nullValues) {
      inverseFeatures.add(MapFeature.ALLOWS_NULL_KEYS);
    }

    inverseFeatures.add(NoRecurse.INVERSE);