/** Let framework take care of internal business. */
  public void loopStart() {
    if (!refreshed.isEmpty()) {
      for (int i = 0; refreshed.size() > i; i++) {
        entityManager.refresh(refreshed.get(i));
      }
      refreshed.clear();
    }

    if (!deleted.isEmpty()) {
      for (int i = 0; deleted.size() > i; i++) {
        Entity e = deleted.get(i);
        groupManager.remove(e);
        entityManager.remove(e);
      }
      deleted.clear();
    }
  }