Null pointer exception at preparedStatement

Question

I am designing simple bank application using servlet and jdbc so while inserting data into database I am getting null pointer exception at preparedStatement

my code for that is

Connection con=null;
     PreparedStatement preparedStatement =null;

     try
     {
     con = DBConnection.createConnection();
     String query = "insert into cst_details(name,surname,aadhar_no,contact_no,address,balance) "
            + "values (?,?,?,?,?,?)";
     preparedStatement = con.prepareStatement(query);
     preparedStatement.setString(1, name);
     preparedStatement.setString(2, surname);
     preparedStatement.setString(3, aadhar_no);
     preparedStatement.setString(4, contact_no);
     preparedStatement.setString(5, address);
     preparedStatement.setString(6,initial_bal);