Formatting MAC address byte array to String

Question

I am using this code to find the MAC address of a machine. This code prints directly the MAC address, but I want to return it as a string. I am completely confused.

please help.

try {

    InetAddress add = InetAddress.getByName("10.123.96.102");
    NetworkInterface ni1 = NetworkInterface.getByInetAddress(add);
    if (ni1 != null) {
        byte[] mac1 = ni1.getHardwareAddress();
        if (mac1 != null) {
            for (int k = 0; k < mac1.length; k++) {
                System.out.format("%02X%s", mac1[k], (k < mac1.length - 1) ? "-" : "");
            }
        } else {
            System.out.println("Address doesn't exist ");
        }
        System.out.println();
    } else {
        System.out.println("address is not found.");
    }
} catch (UnknownHostException e) {
    e.printStackTrace();
} catch (SocketException e) {
    e.printStackTrace();
}

Answer 1

There is no standard text representation for Mac addresses. You just need to convert it to hex and separate the bytes for readability. Here is the function I use in the format of ifconfig on Unix,

public static String getMacAddress(String ipAddr)
        throws UnknownHostException, SocketException {
    InetAddress addr = InetAddress.getByName(ipAddr);
    NetworkInterface ni = NetworkInterface.getByInetAddress(addr);
    if (ni == null)
        return null;

    byte[] mac = ni.getHardwareAddress();
    if (mac == null)
        return null;

    StringBuilder sb = new StringBuilder(18);
    for (byte b : mac) {
        if (sb.length() > 0)
            sb.append(':');
        sb.append(String.format("%02x", b));
    }
    return sb.toString();
}

You just need to change the ':' to '-'.