code: public static void append(File file, Writer writer, String charset) throws IOException {
          appendBuffered(file, writer, charset);
      }
docs: Append the text supplied by the Writer at the end of the File, using a specified encoding.
  
  @param file a File
  @param writer the Writer supplying the text to append at the end of the File
  @param charset the charset used
  @throws IOException if an IOException occurs.
  @since 2.3