code: public void readerFromId(String bucketName, String blobName) throws IOException {
      // [START readerFromId]
      BlobId blobId = BlobId.of(bucketName, blobName);
      try (ReadChannel reader = storage.reader(blobId)) {
        ByteBuffer bytes = ByteBuffer.allocate(64 * 1024);
        while (reader.read(bytes) > 0) {
          bytes.flip();
          // do something with bytes
          bytes.clear();
        }
      }
      // [END readerFromId]
    }
docs: [VARIABLE "my_blob_name"]