How to retrieving data from database using hibernate?

When I'm using this I'm getting java.lang.ClassCastException:
java.lang.String cannot be cast to com.transgenomic.domain.Note error showing

public List<Note> getNoteDescription(Long userId) {
    Session session=sessionFactory.openSession();
    Transaction transaction=session.beginTransaction();
    SQLQuery query=session.createSQLQuery("SELECT n.description"
         + " FROM notes n, users u, tasks t "
         + " where u.userId=t.assignTo AND t.taskId=n.taskId");

    List<Note> notes=query.list();
    System.out.println("***********"+notes);
    transaction.commit();
    session.close();
    return notes;
}