code: public final String encode(byte[] bytes, int off, int len) {
      checkPositionIndexes(off, off + len, bytes.length);
      StringBuilder result = new StringBuilder(maxEncodedSize(len));
      try {
        encodeTo(result, bytes, off, len);
      } catch (IOException impossible) {
        throw new AssertionError(impossible);
      }
      return result.toString();
    }
docs: Encodes the specified range of the specified byte array, and returns the encoded {@code
  String}.