*/
@DoNotMock("Use Optional.of(value) or Optional.absent()")
@GwtCompatible(serializable = true)
@ElementTypesAreNonnullByDefault
public abstract class Optional<T> implements Serializable {
  /**
   * Returns an {@code Optional} instance with no contained reference.
   *
   * <p><b>Comparison to {@code java.util.Optional}:</b> this method is equivalent to Java 8's
   * {@code Optional.empty}.
   */
  public static <T> Optional<T> absent() {

 */
@DoNotMock("Use Optional.of(value) or Optional.absent()")
@GwtCompatible(serializable = true)
@ElementTypesAreNonnullByDefault
public abstract class Optional<T> implements Serializable {
  /**
   * Returns an {@code Optional} instance with no contained reference.
   *
   * <p><b>Comparison to {@code java.util.Optional}:</b> this method is equivalent to Java 8's
   * {@code Optional.empty}.
   */
  public static <T> Optional<T> absent() {

    assertThat(Optional.presentInstances(optionals)).isEmpty();
  }

  public void testPresentInstances_somePresent() {
    List<Optional<String>> optionals =
        ImmutableList.of(Optional.of("a"), Optional.<String>absent(), Optional.of("c"));
    assertThat(Optional.presentInstances(optionals)).containsExactly("a", "c").inOrder();
  }

    assertThat(Optional.presentInstances(optionals)).isEmpty();
  }

  public void testPresentInstances_somePresent() {
    List<Optional<String>> optionals =
        ImmutableList.of(Optional.of("a"), Optional.<String>absent(), Optional.of("c"));
    assertThat(Optional.presentInstances(optionals)).containsExactly("a", "c").inOrder();
  }

            @Override
            public <T> Optional<T> lookupOptional(Class<T> type) {
                try {
                    return Optional.of(injector.getInstance(type));
                } catch (DIException e) {
                    return Optional.empty();
                }
            }

            @Override
            public <T> Optional<T> lookupOptional(Class<T> type, String name) {

    return pickInstance(Currency.getAvailableCurrencies(), Currency.getInstance(Locale.US));
  }

  @Empty
  <T> Optional<T> generateJavaOptional() {
    return Optional.empty();
  }

  @Generates
  <T> Optional<T> generateJavaOptional(T value) {
    return Optional.of(value);
  }

  @Generates
  OptionalInt generateOptionalInt() {
    return OptionalInt.of(generateInt());
  }

                throws InvalidVersionSpecificationException {
            ArtifactSpec dep = createArtifactSpec(id, version, scope, artifact.getScope(), optional);
            return addDependency(dep);
        }

        public ArtifactSpec addDependency(String id, String version, boolean optional)
                throws InvalidVersionSpecificationException {

                        .nonRecursive()
                        .expectResult(MODULE_C),
                scenario("Selected optional project")
                        .activeOptionalProjects(MODULE_B)
                        .expectResult(MODULE_B),
                scenario("Selected missing optional project")
                        .activeOptionalProjects("non-existing-module")
                        .expectResult(

  public void testStream_googleOptional() {
    assertThat(stream(com.google.common.base.Optional.absent())).isEmpty();
    assertThat(stream(com.google.common.base.Optional.of("a"))).containsExactly("a");
  }

  public void testStream_javaOptional() {
    assertThat(stream(java.util.Optional.empty())).isEmpty();
    assertThat(stream(java.util.Optional.of("a"))).containsExactly("a");
  }

  public void testFindLast_refStream() {

        // As a side effect it will log the optional projects that could not be resolved.
        projectSelector.getOptionalProjectsBySelectors(request, session.getAllProjects(), allOptionalSelectors);
    }

    /**
     * Check whether any of the requested optional profiles were not activated or deactivated.
     * @param session the Maven session.
     * @param profileActivation the requested optional and required profiles.
     */