// not MT-safe
        final Queue<UrlQueueImpl<Long>> urlQueueList = dataHelper.getUrlQueueList(oldSessionId);
        // overwrite
        dataHelper.addUrlQueueList(newSessionId, urlQueueList);
        dataHelper.removeUrlQueueList(oldSessionId);
    }

    /*
     * (non-Javadoc)
     *
     * @see org.codelibs.fess.crawler.service.UrlQueueService#add(java.lang.String,
     * java.lang.String)
     */
    @Override

        urlQueueMap.put(sessionId, uqList);
    }

    /**
     * Removes the URL queue for the specified session ID.
     * @param sessionId the session ID
     */
    public synchronized void removeUrlQueueList(final String sessionId) {
        urlQueueMap.remove(sessionId);
    }

    /**
     * Clears all URL queues for all sessions.
     */
    public synchronized void clearUrlQueueList() {