public static String getMACAddress(String interfaceName) {
        try {
            List<NetworkInterface> interfaces = Collections.list(NetworkInterface.getNetworkInterfaces());
            for (NetworkInterface intf : interfaces) {
                if (interfaceName != null) {
                    if (!intf.getName().equalsIgnoreCase(interfaceName)) continue;
                }
                byte[] mac = intf.getHardwareAddress();
                if (mac==null) return "";
                StringBuilder buf = new StringBuilder();
                for (int idx=0; idx<mac.length; idx++)
                    buf.append(String.format("%02X:", mac[idx]));       
                if (buf.length()>0) buf.deleteCharAt(buf.length()-1);
                return buf.toString();
            }
        } catch (Exception ex) { } // for now eat exceptions
        return "";
        /*try {
            // this is so Linux hack
            return loadFileAsString("/sys/class/net/" +interfaceName + "/address").toUpperCase().trim();
        } catch (IOException ex) {
            return null;
        }*/
    }