Interesting Java behavior

I recently was working with a generic list that was being populated by Hibernate.

List fooList = getFooFromHibernate();
for (Foo foo : fooList)
{
// do stuff
}

I was getting ClassCastExceptions while iterating through the list. It took a while to figure out, but the getFooFromHibernate method had a join to the BAR table in it without selecting the fields. Because of this Hibernate dumped a Foo into the list AND a Bar. When I iterated through the list, I got the exception.

This behavior can be caught with integration tests by iterating through the lists retrieved from the database.