src/main/java/com/groupon/uuid/UUID.java
public byte[] getMacFragment() {
        if (getVersion() != 'b')
            return null;

        byte[] x = new byte[6];

        x[0] = 0;
        x[1] = 0;
        x[2] = (byte) (content[6] & 0xF);
        x[3] = content[7];
        x[4] = content[8];
        x[5] = content[9];

        return x;
    }
public byte[] getMacFragment() {
        if (getVersion() != 'b')
            return null;

        byte[] x = new byte[6];

        x[0] = 0;
        x[1] = 0;
        x[2] = (byte) (content[6] & 0xF);
        x[3] = content[7];
        x[4] = content[8];
        x[5] = content[9];

        return x;
    }
Extract MAC address fragment from raw UUID bytes, setting missing values to 0, thus the first 2 and a half bytes
will be 0, followed by 3 and a half bytes of the active MAC address when the UUID was generated.
@return Byte array of UUID fragment, or null for unrecognized format.