errorsField.setAccessible(true);
        ((Queue<?>) errorsField.get(null)).clear();
    }

    // Test addError method
    public void test_addError_withValidMessage() {
        String errorMsg = "Test error message";
        Crawler.addError(errorMsg);

        try {
            Field errorsField = Crawler.class.getDeclaredField("errors");
            errorsField.setAccessible(true);

                logger.error("IndexUpdater is terminated.", t);
                org.codelibs.fess.exec.Crawler.addError(t.getClass().getSimpleName());
            } else if (logger.isInfoEnabled()) {
                logger.info("IndexUpdater is terminated.");
                org.codelibs.fess.exec.Crawler.addError(t.getClass().getSimpleName());
            }
            forceStop();
        } finally {

     * This method is thread-safe and can be called from multiple crawler threads.
     *
     * @param msg the error message to add; ignored if null or blank
     */
    public static void addError(final String msg) {
        if (StringUtil.isNotBlank(msg)) {
            errors.offer(msg);
        }
    }

    /**
     * Command-line options container for the crawler application.