*
 * <ol>
 *   <li>Expose a public method, known as the <i>event subscriber</i>, which accepts a single
 *       argument of the type of event desired;
 *   <li>Mark it with a {@link Subscribe} annotation;
 *   <li>Pass itself to an EventBus instance's {@link #register(Object)} method.
 * </ol>
 *
 * <h2>Posting Events</h2>
 *
 * <p>To post an event, simply provide the event object to the {@link #post(Object)} method. The

         * higher than the current batchLevel so we will now encode
         * that chained message. Before doing so we must increment
         * the batchLevel of the andx message in case it itself is an
         * andx message and needs to perform the same check as above.
         */

        this.andx.batchLevel = this.batchLevel + 1;

        dst[start + ANDX_COMMAND_OFFSET] = this.andxCommand;

        }
    }

    static class SelfRenewingCreds extends BaseCreds {
        @Override
        public CredentialsInternal renew() {
            // Returns itself as the renewed credentials
            return this;
        }
    }

    static class NewRenewingCreds extends BaseCreds {
        @Override
        public CredentialsInternal renew() {

 * the life cycle methods.
 *
 * <h3>Usage Example</h3>
 *
 * <p>Here is a sketch of a service which crawls a website and uses the scheduling capabilities to
 * rate limit itself.
 *
 * {@snippet :
 * class CrawlingService extends AbstractScheduledService {
 *   private Set<Uri> visited;
 *   private Queue<Uri> toCrawl;
 *   protected void startUp() throws Exception {

## IMPORTANT WARNINGS

1.  APIs marked with the `@Beta` annotation at the class or method level are
    subject to change. They can be modified in any way, or even removed, at any
    time. If your code is a library itself (i.e., it is used on the CLASSPATH of
    users outside your own control), you should not use beta APIs unless you
    [repackage] them. **If your code is a library, we strongly recommend using

   * from the resulting text.
   *
   * <p>If the character does not need to be escaped, this method should return {@code null}, rather
   * than a one-character array containing the character itself. This enables the escaping algorithm
   * to perform more efficiently.
   *
   * <p>An escaper is expected to be able to deal with any {@code char} value, so this method should
   * not throw any exceptions.
   *

        // Arrange
        Subject subject = new Subject();
        TestCredentials creds = new TestCredentials("DOMAIN", anonymous, guest, subject, false);

        // Act & Assert
        // unwrap to interface itself should return same instance
        CredentialsInternal unwrapped = creds.unwrap(CredentialsInternal.class);
        assertNotNull(unwrapped, "unwrap to CredentialsInternal returns instance");

 * </ul>
 *
 * <p>
 * The class uses synchronization to ensure thread safety when accessing and modifying the URL queue.
 * It also checks for duplicate URLs before adding them to the queue,
 * both within the queue itself and against previously accessed URLs stored in the {@link MemoryDataHelper}.
 * </p>
 *
 */
/**
 * This class is an implementation of {@link UrlQueueService}.
 */

  /** Returns a serializable converter that always converts or reverses an object to itself. */
  @SuppressWarnings("unchecked") // implementation is "fully variant"
  public static <T> Converter<T, T> identity() {
    return (IdentityConverter<T>) IdentityConverter.INSTANCE;
  }

  /**
   * A converter that always converts or reverses an object to itself. Note that T is now a
   * "pass-through type".
   */

 * the life cycle methods.
 *
 * <h3>Usage Example</h3>
 *
 * <p>Here is a sketch of a service which crawls a website and uses the scheduling capabilities to
 * rate limit itself.
 *
 * {@snippet :
 * class CrawlingService extends AbstractScheduledService {
 *   private Set<Uri> visited;
 *   private Queue<Uri> toCrawl;
 *   protected void startUp() throws Exception {