@GwtCompatible
@ElementTypesAreNonnullByDefault
final class Absent<T> extends Optional<T> {
  static final Absent<Object> INSTANCE = new Absent<>();

  @SuppressWarnings("unchecked") // implementation is "fully variant"
  static <T> Optional<T> withType() {
    return (Optional<T>) INSTANCE;
  }

  private Absent() {}

  @Override
  public boolean isPresent() {
    return false;
  }

@GwtCompatible
@ElementTypesAreNonnullByDefault
final class Absent<T> extends Optional<T> {
  static final Absent<Object> INSTANCE = new Absent<>();

  @SuppressWarnings("unchecked") // implementation is "fully variant"
  static <T> Optional<T> withType() {
    return (Optional<T>) INSTANCE;
  }

  private Absent() {}

  @Override
  public boolean isPresent() {
    return false;
  }

  }

  @MapFeature.Require(value = SUPPORTS_REMOVE, absent = ALLOWS_NULL_VALUE_QUERIES)
  public void testRemoveNullValueForbidden() {
    try {
      multimap().remove(k0(), null);
      fail("Expected NullPointerException");
    } catch (NullPointerException expected) {
      // success
    }
    expectUnchanged();
  }

  @MapFeature.Require(value = SUPPORTS_REMOVE, absent = ALLOWS_NULL_KEY_QUERIES)

  }

  @MapFeature.Require(value = SUPPORTS_PUT, absent = ALLOWS_NULL_VALUES)
  public void testPutAllNullValueSingle_unsupported() {
    multimap().putAll(k1(), Lists.newArrayList((V) null));
    expectUnchanged();
  }

  // In principle, it would be nice to apply these two tests to keys with existing values, too.

  @MapFeature.Require(value = SUPPORTS_PUT, absent = ALLOWS_NULL_VALUES)

public class MultimapEntriesTester<K, V> extends AbstractMultimapTester<K, V, Multimap<K, V>> {
  public void testEntries() {
    assertEqualIgnoringOrder(getSampleElements(), multimap().entries());
  }

  @CollectionSize.Require(absent = ZERO)
  @MapFeature.Require(ALLOWS_NULL_KEYS)
  public void testContainsEntryWithNullKeyPresent() {
    initMultimapWithNullKey();
    assertContains(multimap().entries(), Helpers.mapEntry((K) null, getValueForNullKey()));

  }

  @CollectionSize.Require(absent = ZERO)
  public void testHeadMapExclusive() {
    assertFalse(navigableMap.headMap(a.getKey(), false).containsKey(a.getKey()));
  }

  @CollectionSize.Require(absent = ZERO)
  public void testHeadMapInclusive() {
    assertTrue(navigableMap.headMap(a.getKey(), true).containsKey(a.getKey()));
  }

  @CollectionSize.Require(absent = ZERO)
  public void testTailMapExclusive() {

  @CollectionFeature.Require(SUPPORTS_ADD)
  @CollectionSize.Require(absent = ZERO)
  public void testAdd_supportedPresent() {
    assertTrue("add(present) should return true", getList().add(e0()));
    expectAdded(e0());
  }

  @CollectionFeature.Require(absent = SUPPORTS_ADD)
  @CollectionSize.Require(absent = ZERO)
  /*
   * absent = ZERO isn't required, since unmodList.add() must

@ElementTypesAreNonnullByDefault
public class MultimapPutTester<K extends @Nullable Object, V extends @Nullable Object>
    extends AbstractMultimapTester<K, V, Multimap<K, V>> {
  @MapFeature.Require(absent = SUPPORTS_PUT)
  public void testPutUnsupported() {
    try {
      multimap().put(k3(), v3());
      fail("Expected UnsupportedOperationException");
    } catch (UnsupportedOperationException expected) {
    }
  }

  }

  @CollectionFeature.Require(absent = SUPPORTS_ADD)
  public void testAdd_unsupportedNotPresent() {
    try {
      collection.add(e3());
      fail("add(notPresent) should throw");
    } catch (UnsupportedOperationException expected) {
    }
    expectUnchanged();
    expectMissing(e3());
  }

  @CollectionFeature.Require(absent = SUPPORTS_ADD)
  @CollectionSize.Require(absent = ZERO)

  }

  @MapFeature.Require(absent = ALLOWS_NULL_KEY_QUERIES)
  public void testContainsEntryNullDisallowedBecauseKeyQueriesDisallowed() {
    try {
      multimap().containsEntry(null, v3());
      fail("Expected NullPointerException");
    } catch (NullPointerException expected) {
      // success
    }
  }

  @MapFeature.Require(absent = ALLOWS_NULL_VALUE_QUERIES)