*   <li>Checking if a URL has already been visited.</li>
 *   <li>Generating URL queues from a previous session's access results.</li>
 * </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,

 * It stores URL queues, access results, and URL patterns for inclusion and exclusion.
 * This class is designed to be used in a single-threaded environment or with external synchronization.
 *
 * <p>It uses {@code Map} and {@code Queue} data structures to hold the data. The class provides
 * methods to add, remove, clear, and retrieve data from these structures.
 *