private void sortToDoItems() {
        switch (sorting) {
           case TITLE:
                Collections.sort(this.displayList.getList(), new TitleComparator());
                break;
            case CATEGORY:
                Collections.sort(this.displayList.getList(), new CategoryComparator());
                break;
            case PRIO:
                Collections.sort(this.displayList.getList(), new PrioComparator());
                break;
            case TIME:
                Collections.sort(this.displayList.getList(), new DateComparator());
                break;
        }
    }