@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;
  }

    Set<Object> absentAsSet = Optional.absent().asSet();
    try {
      absentAsSet.add("foo");
      fail();
    } catch (UnsupportedOperationException expected) {
    }
  }

  public void testTransform_absent() {
    assertEquals(Optional.absent(), Optional.absent().transform(Functions.identity()));
    assertEquals(Optional.absent(), Optional.absent().transform(Functions.toStringFunction()));
  }

  @CollectionSize.Require(absent = ZERO)
  public void testReplaceEntry_presentNullValueUnsupported() {
    try {
      getMap().replace(k0(), v0(), null);
      fail("Expected NullPointerException");
    } catch (NullPointerException expected) {
    }
    expectUnchanged();
  }

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

    Set<Object> absentAsSet = Optional.absent().asSet();
    try {
      absentAsSet.add("foo");
      fail();
    } catch (UnsupportedOperationException expected) {
    }
  }

  public void testTransform_absent() {
    assertEquals(Optional.absent(), Optional.absent().transform(Functions.identity()));
    assertEquals(Optional.absent(), Optional.absent().transform(Functions.toStringFunction()));
  }

  @CollectionSize.Require(absent = ZERO)
  public void testReplaceEntry_presentNullValueUnsupported() {
    try {
      getMap().replace(k0(), v0(), null);
      fail("Expected NullPointerException");
    } catch (NullPointerException expected) {
    }
    expectUnchanged();
  }

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

  @MapFeature.Require(value = SUPPORTS_PUT, absent = ALLOWS_NULL_VALUES)
  @CollectionSize.Require(absent = ZERO)
  public void testReplace_presentNullValueUnsupported() {
    try {
      getMap().replace(k0(), null);
      fail("Expected NullPointerException");
    } catch (NullPointerException expected) {
    }
    expectUnchanged();
  }

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

        getMap().getOrDefault(k0(), null));
  }

  public void testGetOrDefault_absent() {
    assertEquals(
        "getOrDefault(absent, def) should return the default value",
        v3(),
        getMap().getOrDefault(k3(), v3()));
  }

  public void testGetOrDefault_absentNullDefault() {
    assertNull("getOrDefault(absent, null) should return null", getMap().getOrDefault(k3(), null));
  }

  @CollectionSize.Require(absent = ZERO)
  public void testSubList_subListRemoveAffectsOriginal() {
    List<E> subList = getList().subList(0, 1);
    subList.remove(0);
    List<E> expected = Arrays.asList(createSamplesArray()).subList(1, getNumElements());
    expectContents(expected);
  }

  @ListFeature.Require(SUPPORTS_REMOVE_WITH_INDEX)
  @CollectionSize.Require(absent = ZERO)

              });
    } catch (UnsupportedOperationException tolerated) {
    }
    expectUnchanged();
  }

  @MapFeature.Require(absent = SUPPORTS_PUT)
  @CollectionSize.Require(absent = ZERO)
  public void testComputeIfPresent_unsupportedPresent() {
    try {
      getMap().computeIfPresent(k0(), (k, v) -> v3());
      fail("Expected UnsupportedOperationException");