private static Optional<String> lookupMessage(int code) {
        int[] codes = WinError.WINERR_CODES;
        String[] msgs = WinError.WINERR_MESSAGES;
        for (int i = 0; i < codes.length; i++) {
            if (codes[i] == code) {
                return Optional.of(msgs[i]);
            }
        }
        return Optional.empty();
    }

`OAuth2PasswordRequestForm` is a class dependency that declares a form body with:

* The `username`.
* The `password`.
* An optional `scope` field as a big string, composed of strings separated by spaces.
* An optional `grant_type`.

/// tip

The OAuth2 spec actually *requires* a field `grant_type` with a fixed value of `password`, but `OAuth2PasswordRequestForm` doesn't enforce it.

    public static final String NAME = "Generic";

    private static final String CI = "CI";

    @Override
    public Optional<CIInfo> detectCI() {
        String ciEnv = System.getenv(CI);
        if (ciEnv != null && !"false".equals(ciEnv)) {
            return Optional.of(new CIInfo() {
                @Override
                public String name() {
                    return NAME;
                }

# OkHttp test platform rules uses optional classes.

    private static final Logger LOGGER = LoggerFactory.getLogger(DefaultBuildResumptionAnalyzer.class);

    @Override
    public Optional<BuildResumptionData> determineBuildResumptionData(final MavenExecutionResult result) {
        if (!result.hasExceptions()) {
            return Optional.empty();
        }

        List<MavenProject> sortedProjects = result.getTopologicallySortedProjects();

        boolean hasNoSuccess =

Notice that the input model is still validated.

So, if you want to receive partial updates that can omit all the attributes, you need to have a model with all the attributes marked as optional (with default values or `None`).

To distinguish from the models with all optional values for **updates** and models with required values for **creation**, you can use the ideas described in [Extra Models](extra-models.md).

  public final Optional<@NonNull E> first() {
    Iterator<E> iterator = getDelegate().iterator();
    return iterator.hasNext() ? Optional.of(iterator.next()) : Optional.absent();
  }

  /**
   * Returns an {@link Optional} containing the last element in this fluent iterable. If the
   * iterable is empty, {@code Optional.absent()} is returned. If the underlying {@code iterable} is

  public final Optional<@NonNull E> first() {
    Iterator<E> iterator = getDelegate().iterator();
    return iterator.hasNext() ? Optional.of(iterator.next()) : Optional.absent();
  }

  /**
   * Returns an {@link Optional} containing the last element in this fluent iterable. If the
   * iterable is empty, {@code Optional.absent()} is returned. If the underlying {@code iterable} is

# Optional Path parameters are not supported...

import java.util.List;
import java.util.Optional;

public class JavaUtil {

    /** A convenience method for getting java home for a version of java and requiring that version for the given task to execute */
    public static String getJavaHome(final int version) {
        List<JavaHome> javaHomes = BuildParams.getJavaVersions();