Question

I’m trying to get the MAC address of a linux system with this code:

try {
  ip = InetAddress.getLocalHost();
  NetworkInterface network = NetworkInterface.getByInetAddress(ip);
  byte[] mac = network.getHardwareAddress();
  // System.out.print("Current MAC address: ");
  for (int i = 0; i < mac.length; i++) {
    is = is + Integer.parseInt(
      String.format("%02X%s", mac[i], (i < mac.length - 1) ? "" : ""),16);
  }
} catch (UnknownHostException e) {
  e.printStackTrace();
} catch (SocketException e) {
  e.printStackTrace();
}

But it just crashes… does anyone know why?

Answer 1

From your comments, clearly network is null, which means that getByInetAddress() could not find an interface with that IP address (see the JavaDocs: http://download.oracle.com/javase/1.5.0/docs/api/java/net/NetworkInterface.html#getByInetAddress(java.net.InetAddress)).