code: public synchronized static boolean isBlacklisted(String ip) {
      if (blacklistCache == null || blacklistCache.isEmpty()) {
        blacklistCache = new HashSet<>();
  
        for (IBlackListProvider provider : BLACKLIST_PROVIDERS) {
          try {
            blacklistCache.addAll(provider.getIPs());
          } catch (IOException e) {
            LOGGER.warn("Error fetching blacklist records", e);
          }
        }
  
      }
      
      return blacklistCache.contains(ip);
    }
docs: Check if the IP is in a blacklist
  @param ip IP to check
  @return whether the ip is blacklisted or not