Is it better to make two database calls or one database call with some java processing?
One database call gets only the relevant data which is to be separated into two different list which requires few lines of java.
Database dips are always an expensive operation. If you can manage with one db fetch and do some java processing, it should be a better and faster choice for you.
But you may have to analyze in your scenarion, which one is turning to be a more efficent choice. I assume singly DB fetch and java processing should be better.
Testing is key. Some questions you may want to ask yourself:
Java Processing is much faster than SQL Fetch, As I had the same problem so I recommend you to fetch single data with some processing, because maybe the time both options take has a minor difference but some Computers take a lot of time to fetch data from DB so I suggest you to just Get single data with some Java Processing.
It all depends on how intensive your processing is and how your database is setup. For instance an Oracle running on a native file system will most likely be more performant then doing the java processing code on your own for complex operations. Note that most build in operations on well known databases are highly optimized and usually very performant.