More elegant way to construct the S3 path name with given options

Question

I have a method that generates the S3 key prefix according to the provided args. However, my gut feeling is that this method is not as elegant as it should be, maybe I just don't have an eye for it. Care to instruct me on how to make this little bit less sketchy?

private String generateFullQualifiedS3KeyPrefix(DataStream dataStream, Options options) {
 String environmentName, applicationName, streamName = applicationName = environmentName = null;
 if (dataStream != null) {
 environmentName = dataStream.getEnvironmentName();
 applicationName = dataStream.getApplicationName();
 streamName = dataStream.getStreamName();
 }
 String year, month, date, groupById = date = month = year = null;
 if (options != null) {
 year = String.valueOf(options.getYear());
 month = String.format("%02d", options.getMonth());
 date = String.format("%02d", options.getDate());
 groupById = options.getGroupById();
 }
 String[] arr = new String[]{environmentName, applicationName, streamName, groupById, year, month, date};
 StringJoiner filePath = new StringJoiner("/");
 for (int i = 0; i < arr.length; i++) {
 if (arr[i] == null) {
 break;
 }
 filePath.add(arr[i]);
 }
 return filePath.toString() + "/";
}

Answer 1

The local variables make this very verbose: each variable is declared, initialized, re-assigned, and referenced. (They each appear 3-4 times in the code.) You could instead accumulate values in a list.

Creating an array that may contain null values, then filtering out the null values in a second step feels like a waste that's easy to avoid. You could instead accumulate non-null values in a list.

Using StringJoiner is efficient to join a string from multiple parts. Then at the end the filePath.toString() + "/" is an inefficient string concatenation that could have been easily avoided by appending an empty string to filePath.

And instead of using StringJoiner, you could use String.join.

Consider this alternative:

private String generateFullQualifiedS3KeyPrefix(DataStream dataStream, Options options) {
 List<String> values = new ArrayList<>();
 if (dataStream != null) {
 values.add(dataStream.getEnvironmentName());
 values.add(dataStream.getApplicationName());
 values.add(dataStream.getStreamName());
 }
 if (options != null) {
 values.add(String.valueOf(options.getYear()));
 values.add(String.format("%02d", options.getMonth()));
 values.add(String.format("%02d", options.getDate()));
 values.add(options.getGroupById());
 }
 values.add("");
 return String.join("/", values);
}