code: private void calculateUploadedAndTotalBytes() {
          uploadedBytes = 0;
  
          for (String filePath : getSuccessfullyUploadedFiles()) {
              uploadedBytes += new File(filePath).length();
          }
  
          totalBytes = uploadedBytes;
  
          for (UploadFile file : params.files) {
              totalBytes += file.length(service);
          }
      }
docs: Calculates the total bytes of this upload task.
  This the sum of all the lengths of the successfully uploaded files and also the pending
  ones.