Is it possible to manipulate post query data with multiple lines of Java?

I have been diving into Jaspersoft Studio for a little bit now and I am trying to manipulate the data I get back from a PostgreSQL query. I know that you can use the Expression Editor to manipulate data, but from my experience, it only allows one line of Java. So, Is there a way to use multiple lines of Java (creating variables or even creating methods) to work with the data?

Thanks for any help on this!