public boolean isRelevant(LinkRelevance link) {
        if (link.getRelevance() <= 0) {
            return false;
        }

        if (useScope && !scope.contains(link.getURL().getHost())) {
            return false;
        }

        if (disallowSitesInRobotsFile && frontier.isDisallowedByRobots(link)) {
            return false;
        }

        Double value = frontier.exist(link);
        if (value != null) {
            return false;
        }

        if (!linkFilter.accept(link)) {
            return false;
        }

        return true;
    }
This class manages the crawler frontier

@author Luciano Barbosa
@version 1.0
ache/src/main/java/achecrawler/link/frontier/FrontierManager.java