Get MAC address on local machine with Java

With all the possible solutions that i've found here and another replies, then i will contribute with my solution. You need to specify a parameter with a String containing "ip" or "mac" depending on what you need to check. If the computer has no interface, then it will return an String containing null, otherwise will return a String containing what you asked for (the ip address or the mac).

How to use it:

System.out.println("Ip: " + GetNetworkAddress.GetAddress("ip"));
System.out.println("Mac: " + GetNetworkAddress.GetAddress("mac"));

Result (if the computer has a network card):

Ip: 192.168.0.10 
Mac: 0D-73-ED-0A-27-44

Result (if the computer doesn't have a network card):

Ip: null
Mac: null

Here's the code:

import java.net.Inet4Address;
import java.net.InetAddress;
import java.net.NetworkInterface;
import java.net.SocketException;
import java.net.UnknownHostException;
import java.util.Enumeration;

public class GetNetworkAddress {

    public static String GetAddress(String addressType) {
        String address = "";
        InetAddress lanIp = null;
        try {

            String ipAddress = null;
            Enumeration<NetworkInterface> net = null;
            net = NetworkInterface.getNetworkInterfaces();

            while (net.hasMoreElements()) {
                NetworkInterface element = net.nextElement();
                Enumeration<InetAddress> addresses = element.getInetAddresses();

                while (addresses.hasMoreElements() && element.getHardwareAddress().length > 0 && !isVMMac(element.getHardwareAddress())) {
                    InetAddress ip = addresses.nextElement();
                    if (ip instanceof Inet4Address) {

                        if (ip.isSiteLocalAddress()) {
                            ipAddress = ip.getHostAddress();
                            lanIp = InetAddress.getByName(ipAddress);
                        }

                    }

                }
            }

            if (lanIp == null)
                return null;

            if (addressType.equals("ip")) {

                address = lanIp.toString().replaceAll("^/+", "");

            } else if (addressType.equals("mac")) {

                address = getMacAddress(lanIp);

            } else {

                throw new Exception("Specify \"ip\" or \"mac\"");

            }

        } catch (UnknownHostException ex) {

            ex.printStackTrace();

        } catch (SocketException ex) {

            ex.printStackTrace();

        } catch (Exception ex) {

            ex.printStackTrace();

        }

        return address;

    }

    private static String getMacAddress(InetAddress ip) {
        String address = null;
        try {

            NetworkInterface network = NetworkInterface.getByInetAddress(ip);
            byte[] mac = network.getHardwareAddress();

            StringBuilder sb = new StringBuilder();
            for (int i = 0; i < mac.length; i++) {
                sb.append(String.format("%02X%s", mac[i], (i < mac.length - 1) ? "-" : ""));
            }
            address = sb.toString();

        } catch (SocketException ex) {

            ex.printStackTrace();

        }

        return address;
    }

    private static boolean isVMMac(byte[] mac) {
        if(null == mac) return false;
        byte invalidMacs[][] = {
                {0x00, 0x05, 0x69},             //VMWare
                {0x00, 0x1C, 0x14},             //VMWare
                {0x00, 0x0C, 0x29},             //VMWare
                {0x00, 0x50, 0x56},             //VMWare
                {0x08, 0x00, 0x27},             //Virtualbox
                {0x0A, 0x00, 0x27},             //Virtualbox
                {0x00, 0x03, (byte)0xFF},       //Virtual-PC
                {0x00, 0x15, 0x5D}              //Hyper-V
        };

        for (byte[] invalid: invalidMacs){
            if (invalid[0] == mac[0] && invalid[1] == mac[1] && invalid[2] == mac[2]) return true;
        }

        return false;
    }

}

UPDATED 02/05/2017: Thanks to @mateuscb on the post How to Determine Internet Network Interface in Java that unfortunately didn't get any upvote on that post before, but he contributed to this update.

The method has been improved to skip virtual machine network cards (most popular VM software)

With Java 6+, you can use NetworkInterface.getHardwareAddress.

Bear in mind that a computer can have no network cards, especially if it's embedded or virtual. It can also have more than one. You can get a list of all network cards with NetworkInterface.getNetworkInterfaces().

Another way is to use an OS command 'getmac' through native code execution.

    Process p = Runtime.getRuntime().exec("getmac /fo csv /nh");
    java.io.BufferedReader in = new java.io.BufferedReader(new  java.io.InputStreamReader(p.getInputStream()));
    String line;
    line = in.readLine();        
    String[] result = line.split(",");

    System.out.println(result[0].replace('"', ' ').trim());

As for the computer being offline, it usually doesn't have an IP assigned, because DHCP is widely used...

And for the question in the title: NetworkInterface.getHardwareAddress()