in the hibernate docs it says doing a unidirectional one to many association is not recommended, and that a join table should be used instead. why is this and how would it be implemented? thanks.

"Unidirectional one to many" is a type of association.
The Hibernate team does not advise against using this type of association.
What you probably read, it that the Hibernate team advises against implementing this kind of association using just 2 tables, with one pointing to the other through a foreign key.

Instead, they probably advised using a third, "relation" table.

Can anybody point me to some sample code that shows how to do this? The description I read in "Java Persistence with Hibernate" was very sketchy, and didn't help me set up the third table.

Also, can anybody explain why I should need a third table to do this? It seems to me all the needed information is in the two tables. My "One" table has IDs for all the entries, and my "Many" table has the ID for each row in the "One" table that owns it.

if i do a bidirectional one to many association, then is it okay to not use a join table?

for example i'm doing:

class Owner {
@OneToMany(cascade = { CascadeType.PERSIST, CascadeType.MERGE, CascadeType.REMOVE}, mappedBy="owner")
getCars()

and then on the many side i have:
Class Car {
getUser()
@ManyToOne
@JoinColumn(name="userId")