doFinal
closes the Decoder.Feed/Encoder.Feed and finalizes the encoding/decoding, such as applying padding (encoding), or processing remaining data in its buffer before dumping them to Decoder.OutFeed/Encoder.OutFeed.
Can only be called once. Any successive calls to doFinal, Decoder.Feed.consume, or Encoder.Feed.consume will be considered an error and throw an EncodingException.
See also
Throws
if isClosed is true, or there was an error encoding/decoding.