code: public static byte [] add(final byte [] a, final byte [] b, final byte [] c) {
      byte [] result = new byte[a.length + b.length + c.length];
      System.arraycopy(a, 0, result, 0, a.length);
      System.arraycopy(b, 0, result, a.length, b.length);
      System.arraycopy(c, 0, result, a.length + b.length, c.length);
      return result;
    }
docs: Concatenate three byte arrays.
  @param a first third
  @param b second third
  @param c third third
  @return New array made from a, b and c