code: public static List<String> parse(String address, String addresses) {
          List<String> result;
          // backwards compatibility - older clients only send a single address in the single address header and don't supply the multi-address header
          if (addresses == null || addresses.isEmpty()) {
              addresses = address;
          }
          if (addresses == null) {
              result = Collections.emptyList();
          }
          else {
              String[] parts = addresses.split(",");
              result = new ArrayList<String>(parts.length);
              for (String part : parts) {
                  part = part.trim();
                  if (NetworkAddress.isValidIPAddress(part)) {
                      result.add(part);
                  }
              }
          }
          return result;
      }
docs: Parse a comma separated string of ip addresses into a list
  Only valid IP address are returned in the list