code: public MultipartUploadRequest addFileToUpload(final String path, final String parameterName,
                                                    final String fileName)
              throws FileNotFoundException, IllegalArgumentException {
          return addFileToUpload(path, parameterName, fileName, null);
      }
docs: Adds a file to this upload request, without setting the content type, which will be
  automatically detected from the file extension. If you want to
  manually set the content type, use {@link #addFileToUpload(String, String, String, String)}.
  @param path Absolute path to the file that you want to upload
  @param parameterName Name of the form parameter that will contain file's data
  @param fileName File name seen by the server side script. If null, the original file name
  will be used
  @return {@link MultipartUploadRequest}
  @throws FileNotFoundException if the file does not exist at the specified path
  @throws IllegalArgumentException if one or more parameters are not valid