Hibernate -> ArrayList cannot be cast to Set

Question

I have a Java EE application and I use Hibernate. The domain objects, I changed the List / ArrayList to Set / HashSet, because it is better to use Sets.

But in my Dao implementation I run into a problem:

public Set<Person> getAllPersons() {
    SessionFactory sessionFactory = HibernateUtil.getSessionFactory();
    Session sess = sessionFactory.getCurrentSession();

    Transaction tx = sess.beginTransaction();
    @SuppressWarnings("unchecked")
    Set<Item> items = (Set<Item>) sess.createQuery("from Item").list();
    tx.commit();

    return items;
}

Here I get an error:

java.lang.ClassCastException: java.util.ArrayList cannot be cast to java.util.Set

What can I do to avoid this error?

Thank you in advance & Best Regards.

Answer 1

List<Item> list = sess.createQuery("from Item").list();
Set<Item> items = new HashSet<Item>(list);  

sess.createQuery("from Item").list(); will return a array list of resulting items, if you need it in Set you can make it as shown in code