code: private void completeMultiPartUpload() throws IOException {
      AmazonClientException lastException;
      CompleteMultipartUploadRequest completeRequest = new CompleteMultipartUploadRequest(mBucketName,
          mKey, mUploadId, mTags);
      do {
        try {
          mClient.completeMultipartUpload(completeRequest);
          LOG.debug("Completed multipart upload for key {} and id '{}' with {} partitions.",
              mKey, mUploadId, mTags.size());
          return;
        } catch (AmazonClientException e) {
          lastException = e;
        }
      } while (mRetryPolicy.attempt());
      // This point is only reached if the operation failed more
      // than the allowed retry count
      throw new IOException("Unable to complete multipart upload with id '"
          + mUploadId + "' to " + mKey, lastException);
    }
docs: Completes multipart upload.