Erro: The resource is not on the build path of a Java Project

public class EventManager {
	public static void main(String[] args) {
		EventManager mgr = new EventManager();
		mgr.createAndStoreEvent("My Event", new Date());
		HibernateUtil.getSessionFactory().close();
		mgr.listEvents();
		
		Session s = HibernateUtil.getSessionFactory().openSession();
		s.beginTransaction();
				
		Event e = new Event();
		e.setTitle("Evento 1");
		e.setDate(new Date());
		s.save(e);//salvou evento
		
		Person p = new Person();
		p.setFirstname("Cristiano");
		p.setLastname("Pena");
		p.setAge(25);
		
		Set set = new HashSet();
		set.add(e);
		
		s.save(p);
		s.update(p);
		s.getTransaction().commit();
		
		
		//mgr.addPersonToEvent(personId, eventId);
	}

	private void createAndStoreEvent(String title, Date theDate) {
		Session session = HibernateUtil.getSessionFactory().getCurrentSession();
		session.beginTransaction();
		Event theEvent = new Event();
		theEvent.setTitle(title);
		theEvent.setDate(theDate);
		session.save(theEvent);
		session.getTransaction().commit();
	}

	private List listEvents() {
		Session session = HibernateUtil.getSessionFactory().getCurrentSession();
		session.beginTransaction();
		List result = session.createQuery("from Event").list();
		session.getTransaction().commit();
		return result;
	}

	private void addPersonToEvent(Long personId, Long eventId) {
		Session session = HibernateUtil.getSessionFactory().getCurrentSession();
		session.beginTransaction();
		Person aPerson = (Person) session
				.createQuery(
						"select p from Person p left join fetch p.events where p.id = :pid")
				.setParameter("pid", personId).uniqueResult(); // Eager fetch
														// detached
		Event anEvent = (Event) session.load(Event.class, eventId);
		session.getTransaction().commit();
		// End of first unit of work
		aPerson.getEvents().add(anEvent); // aPerson (and its collection) is
											// detached
		// Begin second unit of work
		Session session2 = HibernateUtil.getSessionFactory()
				.getCurrentSession();
		session2.beginTransaction();
		session2.update(aPerson); // Reattachment of aPerson
		session2.getTransaction().commit();
	}
}