I am trying to get data from a database in a table with 2 where parameters, When i try to execute this code it gives the error: Parameter not set. I think it is a small mistake
You just need to supply a second parameter for the Datum value:
PreparedStatement s = con.prepareStatement("Select Kaartnummer, Datum, Maaltijd, Prijs FROM Logbestanden WHERE Kaartnummer=? AND Datum=?");
s.setInt(1, Kaartnummer);
s.setInt(2, Datum); // this is what you are missing
rset = s.executeQuery();