* whose next element can always be derived from the previous element. Null elements are not
 * supported, nor is the {@link #remove()} method.
 *
 * <p>Example:
 *
 * {@snippet :
 * Iterator<Integer> powersOfTwo =
 *     new AbstractSequentialIterator<Integer>(1) {
 *       protected Integer computeNext(Integer previous) {
 *         return (previous == 1 << 30) ? null : previous * 2;
 *       }
 *     };
 * }
 *

    }

    /**
     * Checks if there is a previous page.
     * @return True if a previous page exists, false otherwise.
     */
    public boolean isExistPrePage() {
        return existPrePage;
    }

    /**
     * Sets the existence of a previous page.
     * @param existPrePage True if a previous page exists.
     */
    public void setExistPrePage(final boolean existPrePage) {

    }

    /**
     * Checks if a previous page exists.
     *
     * @return true if a previous page exists, false otherwise
     */
    public boolean isExistPrePage() {
        return existPrePage;
    }

    /**
     * Sets whether a previous page exists.
     *
     * @param existPrePage true if a previous page exists, false otherwise
     */

    }

    /**
     * Checks if a previous page exists.
     *
     * @return True if a previous page exists, false otherwise
     */
    public boolean isExistPrePage() {
        return existPrePage;
    }

    /**
     * Sets whether a previous page exists.
     *
     * @param existPrePage True if a previous page exists
     */

    }

    /**
     * Returns true if a previous page exists.
     *
     * @return True if a previous page exists.
     */
    public boolean isExistPrePage() {
        return existPrePage;
    }

    /**
     * Sets whether a previous page exists.
     *
     * @param existPrePage True if a previous page exists.
     */

    }

    /**
     * Checks if a previous page exists.
     *
     * @return true if a previous page exists, false otherwise
     */
    public boolean isExistPrePage() {
        return existPrePage;
    }

    /**
     * Sets whether a previous page exists.
     *
     * @param existPrePage true if a previous page exists, false otherwise
     */

     */
    public void setExistNextPage(final boolean existNextPage) {
        this.existNextPage = existNextPage;
    }

    /**
     * Sets whether a previous page exists.
     *
     * @param existPrevPage true if a previous page exists
     */
    public void setExistPrevPage(final boolean existPrevPage) {
        this.existPrevPage = existPrevPage;
    }

    /**

    }

    /**
     * Checks if there is a previous page.
     * @return True if a previous page exists, false otherwise.
     */
    public boolean isExistPrePage() {
        return existPrePage;
    }

    /**
     * Sets the existence of a previous page.
     * @param existPrePage True if a previous page exists.
     */
    public void setExistPrePage(final boolean existPrePage) {

    }

    /**
     * Returns true if a previous page exists.
     *
     * @return True if a previous page exists.
     */
    public boolean isExistPrePage() {
        return existPrePage;
    }

    /**
     * Sets whether a previous page exists.
     *
     * @param existPrePage True if a previous page exists.
     */

        synchronized (urlQueueList) {
            return !isNewUrl(urlQueue, urlQueueList);
        }
    }

    /**
     * Generates URL queues from a previous session's access results.
     * @param previousSessionId The previous session ID.
     * @param sessionId The current session ID.
     */
    @Override
    public void generateUrlQueues(final String previousSessionId, final String sessionId) {