code: public List<Blob> batchUpdate(String bucketName, String blobName1, String blobName2) {
      // [START batchUpdate]
      Blob firstBlob = storage.get(bucketName, blobName1);
      Blob secondBlob = storage.get(bucketName, blobName2);
      List<Blob> updatedBlobs =
          storage.update(
              firstBlob.toBuilder().setContentType("text/plain").build(),
              secondBlob.toBuilder().setContentType("text/plain").build());
      // [END batchUpdate]
      return updatedBlobs;
    }
docs: [VARIABLE "my_blob_name2"]