Collator Locale German - How to sort accented letters only after the normal ones

i have used Collator to sort an array of objects. But I found out that it treats accented letters like normal ones:

Aktivierung
Änderung
Auszahlung
Bar

instead i would like to have this

Aktivierung
Auszahlung
Änderung
Bar

the accented letter should be placed right after the normal ones. That is also for o/ö and u/ü.

Collator collator = Collator.getInstance(Locale.GERMAN);
...
private void sortDocumentiByCategoria(final Collator collator, List<ListDocumenti> listDocumenti) {
      Collections.sort(listDocumenti, new Comparator<ListDocumenti>(){
          @Override
          public int compare(ListDocumenti arg0, ListDocumenti arg1) {
              return collator.compare(arg0.getDescrizione(), arg1.getDescrizione());
          }
      });
}