this.intervalController = intervalController;
    }

    /**
     * Returns the set of robots.txt URLs.
     * @return The set of robots.txt URLs.
     */
    public Set<String> getRobotsTxtUrlSet() {
        return robotsTxtUrlSet;
    }

    /**
     * Sets the set of robots.txt URLs.
     * @param robotsTxtUrlSet The set of robots.txt URLs.
     */

        } else {
            hostUrl = url;
        }
        final String robotTxtUrl = hostUrl + "/robots.txt";

        // check url
        if (crawlerContext.getRobotsTxtUrlSet().contains(robotTxtUrl)) {
            if (logger.isDebugEnabled()) {
                logger.debug("{} is already visited.", robotTxtUrl);
            }
            return;
        }

        } else {
            hostUrl = url;
        }
        final String robotTxtUrl = hostUrl + "/robots.txt";

        // check url
        if (crawlerContext.getRobotsTxtUrlSet().contains(robotTxtUrl)) {
            if (logger.isDebugEnabled()) {
                logger.debug("{} is already visited.", robotTxtUrl);
            }
            return;
        }