code: public static String hex(long v) {
          final byte[] buf = new byte[2 + 16];
          buf[0] = '0';
          buf[1] = 'x';
          int i = 2 + 16;
          do {
              buf[--i] = HEX[(int) v & 0x0F];
              v >>>= 4;
          } while (v != 0);
          for (/**/; i > 1; i--) {
              buf[i] = '0';
          }
          return new String(buf);
      }
docs: Pretty-prints a {@code long} into a fixed-width hexadecimal number.
  @return A string of the form {@code 0x0123456789ABCDEF}.