*/
@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() {

     * @param active Should the profile be activated?
     * @param optional Can the build continue if the profile does not exist?
     */
    public void addProfileActivation(String id, boolean active, boolean optional) {
        final ActivationSettings settings = ActivationSettings.of(active, optional);
        this.activations.put(id, settings);
    }

        }
        return Optional.empty();
    }

    @Override
    public Optional<Boolean> nonRecursive() {
        if (commandLine.hasOption(CLIManager.NON_RECURSIVE)) {
            return Optional.of(Boolean.TRUE);
        }
        return Optional.empty();
    }

    @Override
    public Optional<Boolean> updateSnapshots() {
        if (commandLine.hasOption(CLIManager.UPDATE_SNAPSHOTS)) {

  public void testEmptiesFirst() {
    Optional<String> empty = Optional.empty();
    Optional<String> abc = Optional.of("abc");
    Optional<String> z = Optional.of("z");

    Comparator<Optional<String>> comparator = emptiesFirst(comparing(String::length));
    testComparator(comparator, empty, z, abc);

    // Just demonstrate that no explicit type parameter is required
    Comparator<Optional<String>> unused = emptiesFirst(naturalOrder());

            Optional<T> o = getter.apply(option);
            if (o.isPresent()) {
                return o;
            }
        }
        return Optional.empty();
    }

    protected Optional<List<String>> collectListIfPresentOrEmpty(Function<O, Optional<List<String>>> getter) {
        int had = 0;
        ArrayList<String> items = new ArrayList<>();
        for (O option : options) {

    public boolean isSelectedVersionKnown() throws OverConstrainedVersionException {
        return versionRange.isSelectedVersionKnown(this);
    }

    @Override
    public void setOptional(boolean optional) {
        this.optional = optional;
    }

            return Optional.of(Boolean.TRUE);
        }
        return Optional.empty();
    }

    @Override
    public Optional<Boolean> showVersion() {
        if (commandLine.hasOption(CLIManager.SHOW_VERSION)) {
            return Optional.of(Boolean.TRUE);
        }
        return Optional.empty();
    }

    @Override
    public Optional<Boolean> quiet() {

        return topDirectory;
    }

    @Override
    public Optional<Path> rootDirectory() {
        return Optional.ofNullable(rootDirectory);
    }

    @Override
    public Optional<InputStream> in() {
        return Optional.ofNullable(in);
    }

    @Override
    public Optional<OutputStream> out() {
        return Optional.ofNullable(out);
    }

    @Override

     * @param active Should the project be activated?
     * @param optional Can the build continue if the project does not exist?
     */
    public void addProjectActivation(String selector, boolean active, boolean optional) {
        final ActivationSettings settings = ActivationSettings.of(active, optional);
        this.activations.add(new ProjectActivationSettings(selector, settings));
    }

        super(options);
    }

    @Override
    public Optional<String> alternatePomFile() {
        return returnFirstPresentOrEmpty(MavenOptions::alternatePomFile);
    }

    @Override
    public Optional<Boolean> offline() {
        return returnFirstPresentOrEmpty(MavenOptions::offline);
    }

    @Override
    public Optional<Boolean> nonRecursive() {