get valid MAC Address

getMACAddress.java

import java.net.NetworkInterface;
import java.util.Enumeration;

public class Main {

    public static void main(String[] args) throws Exception{
        Enumeration<NetworkInterface> nics = NetworkInterface.getNetworkInterfaces();
        while (nics.hasMoreElements()) {
            NetworkInterface ni = nics.nextElement();
            if(ni.getHardwareAddress() != null && ni.isUp() && ni.getHardwareAddress().length == 6) {
                System.out.println("Name            : " + ni.getName());
                System.out.println("Display name    : " + ni.getDisplayName());
                System.out.println("isUp            : " + ni.isUp());
                System.out.println("Hardware address: " + bytesToHexString(ni.getHardwareAddress()));
            }
        }
    }

    public static String bytesToHexString(byte[] bytes) {
        StringBuilder sb = new StringBuilder(2 * bytes.length);
        String s;
        for (byte b : bytes) {
            s = Integer.toHexString(b & 0xff);
            if (s.length() == 1) sb.append('0');
            sb.append(Integer.toHexString(b & 0xff));
        }
        return sb.toString();
    }
}