public List<ExameDAO> getExames() {
        try {
            EntityManager em = conecta();
            if (em != null) {
                Query q = em.createQuery("SELECT p FROM Exame p");
                List<Exame> resultado = q.getResultList();
                List<ExameDAO> exames = new ArrayList<ExameDAO>();
                for (Exame p : resultado) {
                    exames.add(new ExameDAO(p.getIdExame(), p.getNome(), p.getValor()));
                }
                return exames;
            }
            return null;
        } catch (Exception e) {
            return null;
        }
    }