InterfaceAddress.equals contains this:

if ((address != null & cmp.address == null) ||
    (!address.equals(cmp.address)))
    return false;
if ((broadcast != null & cmp.broadcast == null) ||
    (!broadcast.equals(cmp.broadcast)))
    return false;

if address == null, or broadcast == null, NPE will be thrown.  broadcast ==
null can be tested by running this test:

try {
   Enumeration<NetworkInterface> networkInterfaces =
      NetworkInterface.getNetworkInterfaces();

   while (networkInterfaces.hasMoreElements()) {
      NetworkInterface networkInterface = networkInterfaces.nextElement();

      List<InterfaceAddress> interfaceAddresses =
         networkInterface.getInterfaceAddresses();

      for (InterfaceAddress interfaceAddress : interfaceAddresses) {
         interfaceAddress.equals(interfaceAddress);
      }
   }
} catch (SocketException ex) {
   ex.printStackTrace();
}

When the loopback interface address is reached, NPE will be thrown for the
broadcast test.  I'm not sure if you can get an interface address with a null
address.

This has been fixed in JDK 7.