@Override
        public Object getValueAt(int rowIndex, int columnIndex) {
            if (briefe == null || rowIndex >= briefe.size()) {
                return null;
            }

            BeitragBrief row = briefe.get(rowIndex);
            SimpleDateFormat formatter = new SimpleDateFormat("dd.MM.yyyy");
            SimpleDateFormat formatterWithTime = new SimpleDateFormat(
                    "dd.MM.yyyy HH:mm:ss");
            switch (columnIndex) {
            case ID_COLUMN_INDEX:
                return row.getBriefId();
            case DATEINAME_COLUMN_INDEX:
                return row.getDateiname();
            case DATUM_COLUMN_INDEX:
                if (row.getDatum() == null) {
                    return "";
                } else {
                    return formatter.format(row.getDatum());
                }
            case TYP_COLUMN_INDEX:
                return row.getTyp();
            case KOMPILIERUNG_COLUMN_INDEX:
                if (row.getKompiliert() == null) {
                    return "";
                } else {
                    return formatterWithTime.format(row.getKompiliert());
                }
            default:
                return null;
            }
        }