public void insertRobotRules(LinkRelevance link, SimpleRobotRules robotRules) {
        if (link == null || robotRules == null) {
            throw new NullPointerException("Link argument or robot rules argument cannot be null");
        }
        String hostname = link.getURL().getHost();
        robotRulesMap.put(hostname, new SerializableRobotRules(robotRules));
    }
Inserts the robot rules object into the HashMap

@param link
@param robotRules
@throws NullPointerException
            when either of the argument is null
ache/src/main/java/achecrawler/link/frontier/Frontier.java