public synchronized void logUnavailableHost(URL url) {
    if (this.offlineMode) return;

    if (url == null) {
      String message = Logging.getMessage("nullValue.URLIsNull");
      Logging.error(message);
      throw new IllegalArgumentException(message);
    }

    String hostName = url.getHost();
    HostInfo hi = this.hostMap.get(hostName);
    if (hi != null) {
      if (!hi.isUnavailable()) {
        hi.logCount.incrementAndGet();
        if (hi.isUnavailable()) // host just became unavailable
        this.firePropertyChange(NetworkStatus.HOST_UNAVAILABLE, null, url);
      }
      hi.lastLogTime.set(System.currentTimeMillis());
    } else {
      hi = new HostInfo(this.attemptLimit.get(), this.tryAgainInterval.get());
      hi.logCount.set(1);
      if (hi.isUnavailable()) // the attempt limit may be as low as 1, so handle that case here
      this.firePropertyChange(NetworkStatus.HOST_UNAVAILABLE, null, url);
      this.hostMap.put(hostName, hi);
    }

    this.lastUnavailableLogTime.set(System.currentTimeMillis());
  }
  public boolean isHostUnavailable(URL url) {
    if (this.offlineMode) return true;

    if (url == null) {
      String message = Logging.getMessage("nullValue.URLIsNull");
      Logging.error(message);
      throw new IllegalArgumentException(message);
    }

    String hostName = url.getHost();
    HostInfo hi = this.hostMap.get(hostName);
    if (hi == null) return false;

    if (hi.isTimeToTryAgain()) {
      hi.logCount.set(0); // info removed from table in logAvailableHost
      return false;
    }

    return hi.isUnavailable();
  }