private void updateRosterList() {
		availableRosters = 0;
		if ((rosterListModel == null) || (MainWindow.rosterDB == null))
			return;
		rosterListModel.removeAllElements();
		for (Roster r: MainWindow.rosterDB.getRosters()) {
	    	if (r.isAvailableAt (targetDay.getTime())) {
	    		rosterListModel.addElement( new RosterComponent(r));
	    		availableRosters++;
	    	}
	    }
		tfRoster.setText(MainWindow.tripDB.getRosterCount(targetDay.getTime()) + "/" + availableRosters);
	}