@Override
        public String getColumnName(int column) {
            if (column == CHECK_COLUMN_INDEX) {
                return "Ausgewählt";
            }

            String line1, line2;
            switch (column) {
            case ID_MANDAT_COLUMN_INDEX:
                line1 = "MandatsID";
                break;
            case IBAN_MANDAT_COLUMN_INDEX:
                line1 = "IBAN";
                break;
            case BIC_MANDAT_COLUMN_INDEX:
                line1 = "BIC";
                break;
            case KONTOINH_MANDAT_COLUMN_INDEX:
                line1 = "Kontoinhaber";
                break;
            default:
                line1 = "";
            }
            switch (column) {
            case NR_RECH_COLUMN_INDEX:
                line2 = "Rechnungsnummer";
                break;
            case DATUM_RECH_COLUMN_INDEX:
                line2 = "Datum";
                break;
            case NAME_RECH_COLUMN_INDEX:
                line2 = "Name";
                break;
            case BETRAG_RECH_COLUMN_INDEX:
                line2 = "Betrag";
                break;
            default:
                line2 = "";
            }
            return "<html>" + line1 + "<br>" + line2;

        }