code: private void uploadPart() throws IOException {
      if (mFile == null) {
        return;
      }
      mLocalOutputStream.close();
      int partNumber = mPartNumber.getAndIncrement();
      File newFileToUpload = new File(mFile.getPath());
      mFile = null;
      mLocalOutputStream = null;
      UploadPartRequest uploadRequest = new UploadPartRequest()
          .withBucketName(mBucketName)
          .withKey(mKey)
          .withUploadId(mUploadId)
          .withPartNumber(partNumber)
          .withFile(newFileToUpload)
          .withPartSize(newFileToUpload.length());
      execUpload(uploadRequest);
    }
docs: Uploads part async.