JTextField Limit Character

Question

I have a JTextField named for Reservation ID on JFrame connected to MySQL database. Whenever I add a new passenger in the database, the JTextField should automatically generate a new Reservation ID for me in the JTextField based on an auto increment before I enter the passenger names and other details in the other textfields.

My code:

    resId = new JTextField();
    try{
        rs = stt.executeQuery("select ReservID as last_id from passenger");
        int lastid = rs.getInt("last_id");
        lastid++;
        resId.setText(String.valueOf(last_id));

    }catch(Exception e){
        JOptionPane.showMessageDialog(null, "cannot retrieve");
    }
    resId.setBounds(432, 178, 126, 22);
    frame.getContentPane().add(resId);
    resId.setColumns(10);

The last row of my column RevervID has value of 003. When I run the form, it should display me 004 in the Reservation ID textfield How do I achieve that ? Please help.. Thanks

The texfield in the image link below http://i.imgbox.com/wcf9KicU.png

Answer 1

First find out the maximum id using database query-> Select max(id) from mytable

Store the maximum id in a variable-> int max_id= max_id_from_database;

Increment max_id by one-> max_id++;

add max_id value to your JTextField-> myJTextField.setText("" + max_id);

Edited: According to your code (just add max before ReservID and add rs.next() in a if condition and ReservID must be integer in your database).

 resId = new JTextField();
    try{
        rs = stt.executeQuery("select max(ReservID) as last_id from passenger");
        if(rs.next()){
        int lastid = rs.getInt("last_id");
        lastid++;
        resId.setText(String.valueOf(last_id));
        }

    }catch(Exception e){
        JOptionPane.showMessageDialog(null, "cannot retrieve");
    }