@Override
  public  boolean isIn(String ipAddress) {
    if (ipAddress == null || addressList == null) {
      return false;
    }
    return addressList.includes(ipAddress);
  }
@Test
  public void testNullIP() throws IOException {

    String[] ips = {"10.119.103.112", "10.221.102.0/23"};
    createFileWithEntries ("ips.txt", ips);

    IPList ipList = new FileBasedIPList("ips.txt");

    assertFalse ("Null Ip is in the list",
        ipList.isIn(null));
  }