/**
     * QueueHolder holds the waiting and crawling queues.
     */
    protected static class QueueHolder {
        /**
         * Constructs a new QueueHolder.
         */
        public QueueHolder() {
            // Default constructor
        }

        /**
         * The queue for URLs waiting to be crawled.
         */
        protected Queue<OpenSearchUrlQueue> waitingQueue = new ConcurrentLinkedQueue<>();

 *   <li>Deleting URL queues associated with a session.</li>
 *   <li>Deleting all URL queues.</li>
 *   <li>Offering a list of URLs to the queue, ensuring duplicates are not added.</li>
 *   <li>Polling (retrieving and removing) a URL from the queue.</li>
 *   <li>Saving the session (currently a no-op).</li>
 *   <li>Checking if a URL has already been visited.</li>
 *   <li>Generating URL queues from a previous session's access results.</li>

    /**
     * Deletes all URL queues.
     */
    void deleteAll();

    /**
     * Offers all URL queues.
     *
     * @param sessionId The session ID.
     * @param newUrlQueueList The list of new URL queues.
     */
    void offerAll(String sessionId, List<QUEUE> newUrlQueueList);

    /**
     * Polls a URL queue.
     *
     * @param sessionId The session ID.

        super();
    }

    /**
     * Clears all URL queues and session data.
     */
    public void clear() {
        urlQueueMap.clear();
        sessionMap.clear();
    }

    /**
     * Returns the URL queue for the specified session ID.
     * Creates a new queue if one doesn't exist.
     * @param sessionId the session ID
     * @return the URL queue for the session
     */

        this.filterIndex = filterIndex;
    }

    /**
     * Returns the number of queue shards.
     * @return The number of queue shards.
     */
    public int getQueueShards() {
        return queueShards;
    }

    /**
     * Sets the number of queue shards.
     * @param queueShards The number of queue shards.
     */
    public void setQueueShards(final int queueShards) {

        }
        log(logHelper, LogType.FINISHED_THREAD, crawlerContext);
    }

    /**
     * Adds sitemaps from robots.txt to the crawling queue.
     * @param urlQueue The URL queue to add sitemaps to.
     */
    protected void addSitemapsFromRobotsTxt(final UrlQueue<?> urlQueue) {
        final String[] sitemaps = crawlerContext.removeSitemaps();
        if (sitemaps != null) {

 *   crawler.close();
 * </pre>
 */
public class Crawler implements Runnable, AutoCloseable {

    private static final Logger logger = LogManager.getLogger(Crawler.class);

    /**
     * Service for managing URL queues during crawling.
     */
    @Resource
    protected UrlQueueService<UrlQueue<?>> urlQueueService;

    /**
     * Service for managing access result data.
     */
    @Resource

/**
 * The UrlQueue interface represents a queue of URLs to be processed by a web crawler.
 * It provides methods to get and set various properties of a URL queue entry.
 *
 * @param <IDTYPE> the type of the identifier for the URL queue entry
 */
public interface UrlQueue<IDTYPE> {

    /**
     * Retrieves the unique identifier of the URL queue.
     *
     * @return the unique identifier of type IDTYPE.
     */

        return URL_QUEUE_THREAD_LOCAL.get();
    }

    /**
     * Sets the URL queue for the current thread. If the provided URL queue is null,
     * the URL queue for the current thread is removed.
     *
     * @param urlQueue the URL queue to be set for the current thread, or null to remove the URL queue
     */
    public static void setUrlQueue(final UrlQueue<?> urlQueue) {
        if (urlQueue == null) {

    /** The metadata associated with the URL queue. */
    protected String metaData;

    /** The encoding of the URL queue. */
    protected String encoding;

    /** The parent URL of the current URL in the queue. */
    protected String parentUrl;

    /** The depth of the URL in the queue. */
    protected Integer depth;

    /** The last modified timestamp of the URL in the queue. */
    protected Long lastModified;