public void exec()
	{
		PrintStream out = System.out;
		String stadt_name = askUserForCity();
		CityInfo cityInfo = null;
		try {
			cityInfo = lookUpCity(stadt_name);
			if( cityInfo == null)
			{
				out.println("city not found!");
				return;
			}
			
		}
		catch(SQLException e) {
			out.println("ERROR: looking up city failed: " + e.getMessage());
		}
		Date date = null;
		int station_id = -1;
		try {
			date = askUserForDate();
			//System.out.println("eingegebenes Datum: " + date.toString());
			station_id = lookupNextStation(cityInfo);
		}
		catch(SQLException e) {
			out.println("ERROR: failed while searching for a wetterstation: " + e.getMessage());
		}
		
		MessungInfo messung = null;
		try {
			messung = lookupMessung(station_id,date);
			if( messung == null)
			{
				out.println("keine Entsprechende Messung gefunden!");
				System.exit(0);
			}
		}
		catch(SQLException e) {
			out.println("ERROR: failed while searching for wetterdaten: " + e.getMessage());
		}
		printMessung(messung);
	}