/**
   * Determines and stores the network sites to test for public network connectivity. The sites are
   * drawn from the JVM's gov.nasa.worldwind.avkey.NetworkStatusTestSites property ({@link
   * AVKey#NETWORK_STATUS_TEST_SITES}). If that property is not defined, the sites are drawn from
   * the same property in the World Wind or application configuration file. If the sites are not
   * specified there, the set of sites specified in {@link #DEFAULT_NETWORK_TEST_SITES} are used. To
   * indicate an empty list in the JVM property or configuration file property, specify an empty
   * site list, "".
   */
  protected void establishNetworkTestSites() {
    String testSites = System.getProperty(AVKey.NETWORK_STATUS_TEST_SITES);

    if (testSites == null)
      testSites = Configuration.getStringValue(AVKey.NETWORK_STATUS_TEST_SITES);

    if (testSites == null) {
      this.networkTestSites.addAll(Arrays.asList(DEFAULT_NETWORK_TEST_SITES));
    } else {
      String[] sites = testSites.split(",");
      List<String> actualSites = new ArrayList<String>(sites.length);

      for (String site : sites) {
        site = WWUtil.removeWhiteSpace(site);
        if (!WWUtil.isEmpty(site)) actualSites.add(site);
      }

      this.setNetworkTestSites(actualSites);
    }
  }