How to select item name from jList in netbeans?

Question

i have been trying to retrive data from mysql in the list and that is working fine but the problem is i'm not able to select the name of the list .. i want to select name (not index or value) so that i can complete my where clause

Here is my Code :-

private void proceed(){

    PreparedStatement stmt = null;
    Connection conn = null;
    ResultSet rs=null;

    String i = jList1.getSelectedValue();




    try    {

     Class.forName("java.sql.DriverManager");

     conn = DriverManager.getConnection ("jdbc:mysql://localhost:3306/hotel","root","root");

      stmt = conn.prepareStatement("select * from hotelbookings where GuestName = '"+i+"'");

    rs = stmt.executeQuery();

    if (rs.next()){

    String BN = rs.getString("BookNo");
    String GN = rs.getString("GuestName");
    String AD = rs.getString("Address");
    String NOD = rs.getString("No_of_Days");
    String PN = rs.getString("PhoneNo");
    String ID = rs.getString("ID_Proof");
    String CN = rs.getString("Country");
    String ARD = rs.getString("Arival_Date");
    String DRD = rs.getString("Departure_Date");

    NewJFrame1_1 second = new NewJFrame1_1(BN,GN,AD,NOD,PN,ID,CN,ARD,DRD);
    second.setVisible(true);

    }

} catch(Exception e){
 JOptionPane.showMessageDialog(null, e);
}


}

Here is the image of my list ..Show List retreives the data from mysql ..and proceed button is used to take the selected name for modification

Here is The code for Show List Button:-

private void fillList(){

        PreparedStatement stmt = null;
        Connection conn = null;


         try    {
         Class.forName("java.sql.DriverManager");

         conn = DriverManager.getConnection ("jdbc:mysql://localhost:3306/hotel","root","root");

          stmt = conn.prepareStatement("select GuestName from hotelbookings");

         stmt.executeQuery();

             ResultSet rs = stmt.getResultSet();
             int i =0;
             DefaultListModel info = new DefaultListModel();

             while (rs.next()){
                 String[] data = new String[100];
                 data[i] = rs.getString("GuestName");
                 jList1.setModel(info);
                 info.addElement(data[i]);
                 i = i + 1;
                 jList1 = new JList(info);
             }

}
      catch(Exception e){

                JOptionPane.showMessageDialog (this, e.getMessage());
}




    }

fillList class:-

private void jButton2ActionPerformed(java.awt.event.ActionEvent evt) {

     fillList();

}

Answer 1

private void fillList(){

PreparedStatement stmt = null;
Connection conn = null;

try    {
    Class.forName("java.sql.DriverManager");
    conn = DriverManager.getConnection ("jdbc:mysql://localhost:3306/hotel","root","root");
    stmt = conn.prepareStatement("select GuestName from hotelbookings");
    stmt.executeQuery();
    ResultSet rs = stmt.getResultSet();
    int i =0;
    DefaultListModel info = new DefaultListModel();

    while (rs.next()){
        String[] data = new String[100];
        data[i] = rs.getString("GuestName");
        info.addElement(data[i]);
        i = i + 1;
    }
    jList1 = new JList(info);
} catch(Exception e){
    JOptionPane.showMessageDialog (this, e.getMessage());
}

}

Answer 2

Well, the basic problem with the fillList as far as I can tell from your posted code is the while loop. You create a new JList for every loop. This will make invalid (or should I say dirty ) the jList1 reference you have in the proceed method. You should not create a new JList every time. Just keep the same list for every loop. Do not even change it outside the loop. Just keep it the same and update its model every time.

To update the model, you have at least the following two options:

1. Create a new model every time, update it (ie add all elements you want in it) and call jList1.setModel(your_created_model) .
2. Set the model of the JList to DefaultListModel once (on construction time for example), and then in each fillList method call:
   1. Get the model from the list itself (via getModel() ). You know it's a DefaultListModel so you can safely cast it to one.
   2. Remove all elements from the model (vis removeAllElements() ).
   3. Add all new elements from the ResultSet to the model.

Take for example the following code:

import java.awt.BorderLayout;
import java.awt.Dimension;
import javax.swing.DefaultListModel;
import javax.swing.JButton;
import javax.swing.JFrame;
import javax.swing.JList;
import javax.swing.JOptionPane;
import javax.swing.JPanel;
import javax.swing.JScrollPane;
import javax.swing.ListSelectionModel;

public class Main {
    public static void fillList(final JList<String> list) {
        final DefaultListModel<String> model = (DefaultListModel<String>) list.getModel(); //Step 1: Get the model and cast it to DefaultListModel.
        model.removeAllElements(); //Step 2: Remove all elements from the model.
        final double rand = Math.random();
        for (int i = 0; i < 10; ++i)
            model.addElement("name " + Math.round((1 + i) * rand * 100)); //Step 3: Fill the model with new elements.
    }

    public static void proceed(final JList<String> list) {
        JOptionPane.showMessageDialog(list, "You selected: \"" + list.getSelectedValue() + "\"!");
        //Here you have the selected value approprietly to do whatever you like with...
    }

    public static void main(final String[] args) {
        final JList<String> names = new JList<>(new DefaultListModel<>()); //Do not forget to set the ListModel of the list to DefaultListModel!

        //List initialization:
        names.setSelectionMode(ListSelectionModel.SINGLE_SELECTION);
        fillList(names);

        //Creating the buttons:
        final JButton fill = new JButton("Fill"),
                      proceed = new JButton("Proceed");

        //Adding listeners:
        fill.addActionListener(e -> fillList(names));
        proceed.addActionListener(e -> proceed(names));

        //Creating buttons' panel:
        final JPanel buttons = new JPanel();
        buttons.add(fill);
        buttons.add(proceed);

        //Scroll pane of list:
        final JScrollPane scroll = new JScrollPane(names);
        scroll.setPreferredSize(new Dimension(400, 200));

        //Main panel:
        final JPanel contents = new JPanel(new BorderLayout());
        contents.add(scroll, BorderLayout.CENTER);
        contents.add(buttons, BorderLayout.PAGE_END);

        //Frame:
        final JFrame frame = new JFrame("List of MesureTypes.");
        frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
        frame.getContentPane().add(contents);
        frame.pack();
        frame.setLocationRelativeTo(null);
        frame.setVisible(true);
    }
}

It utilizes the second option (refilling the model each time).