removeObjects

   private void removeObjects() {
        CriteriaBuilder builder = this.em.getCriteriaBuilder();
        CriteriaQuery<Town> criteria = builder.createQuery(Town.class);
        Root<Town> r = criteria.from(Town.class);
        criteria.select(r);
        List<Town> towns =  this.em.createQuery(criteria).getResultList();
        for (Town t : towns) {
            if (t.getName().length() > 5) {
                this.em.detach(t);
            } else {
                t.setName(t.getName().toLowerCase());
                this.em.persist(t);
            }
        }
    }