Your PL/SQL needs to return something.
You have two (2) options:
Declare an "out" parameter in your stored procedure.
Use a stored function instead of a stored procedure.
Your implementation will depend on the version of java you are using, the version of Oracle database you are using and the version of Oracle JDBC driver you are using.
Unfortunately, I could not ascertain these details from your post.
I suggest you search the internet for:
oracle jdbc return ref cursor
subject: Fetching multiple rows through stored procedure by preparecall method