code: public static String encode(byte[] bytes)
      {
          StringBuilder sb = new StringBuilder(bytes.length << 1);
          for (byte aByte : bytes)
          {
              sb.append(convertDigit(aByte >> 4));
              sb.append(convertDigit(aByte & 0x0f));
          }
          return sb.toString();
      }
docs: Convert a byte array into a printable format containing a
  String of hex digit characters (two per byte).
  
  @param bytes array representation