code: public static String getMD5Checksum(String filename) {
         try {
             byte[] b = createChecksum(filename);
             String result = "";
  
             for (int i=0; i < b.length; i++) {
                 result += Integer.toString( ( b[i] & 0xff ) + 0x100, 16).substring( 1 );
             }
             return result;
         } catch (Exception e){
             return "";
         }
     }
docs: a byte array to a HEX string