Depending on your association/relationship, a join table is not required. It would be required in a many to many scenario, but not many to one or one to many.
There are a few things to bear in mind when writing
java classes that will be mapped with Hibernate to a relational database. You generally need a no args constructor (although due to Hibernate's trickery) this doesnt need to be public.
You will also need to think about identity of hibernate persisted objects. This may mean adding an indentity property that you otherwise wouldnt need to access.
Hope this helps.
Rosco