if (instance != null) {
      return (ListenableFuture<V>) instance;
    }
    return new ImmediateCancelledFuture<>();
  }

  /**
   * Executes {@code callable} on the specified {@code executor}, returning a {@code Future}.
   *
   * @throws RejectedExecutionException if the task cannot be scheduled for execution
   * @since 28.2
   */

    /**
     * Flag indicating whether the crawling process should be aborted.
     */
    private final boolean abort;

    /**
     * Creates a new DataStoreCrawlingException with the specified URL, message, and cause.
     * The abort flag is set to false by default.
     *
     * @param url the URL where the crawling error occurred
     * @param message the error message

 * and committing changes to the search index.
 */
public interface IndexUpdateCallback {

    /**
     * Stores a document in the search index with the specified parameters and data.
     *
     * @param paramMap the data store parameters containing configuration and metadata
     * @param dataMap the document data to be indexed as key-value pairs
     */

    /** The action class that requires specific user roles */
    private final Class<? extends RootAction> actionClass;

    /**
     * Constructs a new UserRoleLoginException with the specified action class.
     *
     * @param actionClass the action class that requires specific user roles
     */
    public UserRoleLoginException(final Class<? extends RootAction> actionClass) {

    protected ShutdownListener shutdownListener;

    /**
     * Default constructor.
     */
    public JobExecutor() {
        // Default constructor
    }

    /**
     * Executes a script with the specified script type and content.
     *
     * @param scriptType the type of script to execute
     * @param script the script content to execute
     * @return the result of script execution
     */

 *
 */
public class QueryParser {

    /**
     * Default constructor.
     */
    public QueryParser() {
        // Default constructor
    }

    /** The default field to search in when no field is specified in the query */
    protected String defaultField = Constants.DEFAULT_FIELD;

    /** The analyzer used to analyze query terms */
    protected Analyzer analyzer = new WhitespaceAnalyzer();

      afe.initCause(t);
      throw afe;
    }
  }

  /**
   * Delays, via Thread.sleep, for the given millisecond delay, but if the sleep is shorter than
   * specified, may re-sleep or yield until time elapses.
   */
  @SuppressWarnings("ThreadPriorityCheck") // TODO: b/175898629 - Consider onSpinWait?
  static void delay(long millis) throws InterruptedException {

      return addTo.addAll(c);
    }
    return Iterators.addAll(addTo, checkNotNull(elementsToAdd).iterator());
  }

  /**
   * Returns the number of elements in the specified iterable that equal the specified object. This
   * implementation avoids a full iteration when the iterable is a {@link Multiset} or {@link Set}.
   *

/**
 * Methods factored out so that they can be emulated differently in GWT.
 *
 * @author Chris Povirk
 */
final class Platform {
  /** Serializes and deserializes the specified object (a no-op under GWT). */
  @SuppressWarnings("unchecked")
  static <T> T reserialize(T object) {
    return checkNotNull(object);
  }

  private Platform() {}

 */
public class UnsupportedEncodingRuntimeException extends ClRuntimeException {

    private static final long serialVersionUID = 1L;

    /**
     * Creates a new {@link UnsupportedEncodingRuntimeException} with the specified cause.
     *
     * @param cause
     *            the cause
     */
    public UnsupportedEncodingRuntimeException(final UnsupportedEncodingException cause) {