return urlQueueList.poll();
        }
    }

    /*
     * (non-Javadoc)
     *
     * @see
     * org.codelibs.fess.crawler.service.UrlQueueService#saveSession(java.lang.String)
     */
    @Override
    public void saveSession(final String sessionId) {
        // NOP
    }

    /*
     * (non-Javadoc)
     *
     * @see org.codelibs.fess.crawler.service.UrlQueueService#visited(UrlQueue)

     * @return The URL queue.
     */
    QUEUE poll(String sessionId);

    /**
     * Saves the session.
     *
     * @param sessionId The session ID.
     */
    void saveSession(String sessionId);

    /**
     * Checks if a URL has been visited.
     *
     * @param urlQueue The URL queue.
     * @return true if the URL has been visited, otherwise false.
     */