code: private FileUpload prepareFileUpload(@NonNull String encoding) {
          FileUpload actualFileUpload = mFileUpload;
          if (!encoding.equalsIgnoreCase(mFileUpload.getHeaderEncoding())) {
              actualFileUpload = new FileUpload(mFileItemFactory);
              actualFileUpload.setSizeMax(mFileUpload.getSizeMax());
              actualFileUpload.setFileSizeMax(mFileUpload.getFileSizeMax());
              actualFileUpload.setHeaderEncoding(encoding);
          }
          return actualFileUpload;
      }
docs: Determine an appropriate FileUpload instance for the given encoding.
  
  <p>Default implementation returns the shared FileUpload instance if the encoding matches, else creates a new
  FileUpload instance with the same configuration other than the desired encoding.
  
  @param encoding the character encoding to use.
  
  @return an appropriate FileUpload instance.