code: public static String createReadableString(String bucketName, String objectName) {
      if (bucketName == null && objectName != null) {
        throw new IllegalArgumentException(
            String.format("Invalid bucketName/objectName pair: gs://%s/%s", bucketName, objectName));
      }
      // TODO(user): Unify this method with other methods that convert bucketName/objectName
      // to a URI; maybe use the single slash for compatibility.
      StringBuilder result = new StringBuilder("gs://");
      if (bucketName != null) {
        result.append(bucketName);
      }
      if (objectName != null) {
        result.append('/').append(objectName);
      }
      return result.toString();
    }
docs: Helper for standardizing the way various human-readable messages in logs/exceptions that refer
  to a bucket/object pair.