DSS is a Java-based application but it is not apparently clear what you are looking for exactly. Could you clarify what you mean and/or provide more details about your particular use case?
The requirement was to do admin related activities using Java application on DSS. As suggested, I followed the REST APIs documentation and was able to complete it.
We have a requirement where application is Java-based and we would like to create users in Dataiku using Java based application.
Therefore, looking for a java package which can interact with dataiku to create, update and delete user.
You should be able to accomplish this by leveraging the REST APIs that are available in DSS. For example, you can use these APIs to programmatically create, update, and delete users as you've mentioned. More information about these particular APIs can be found in our API documentation here: https://doc.dataiku.com/dss/api/7.0/rest/#security-users
I hope that this helps but please let me know if this isn't what you're looking for!