Displaying one JDialog window at a time

Question

Hi,
I'm having some trouble trying to write a code where only one JDialog window appears at one time.
-so when one jdialog box appears, no other jdialog can appear
-I was thinking about using a boolean but it didn't work at all
Here's my code:
iimport javax.swing.*;
import java.awt.event.*;
public class Data extends JFrame
     JMenuItem existingRental;
     JMenuItem newRental;
     boolean one = true;
     public Data(){
          createMainMenu();
          setSize(350, 100);
          setVisible(true);
          setLocationRelativeTo(null);
          setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
     public static void main(String[] args){
          new Data();
     private void createMainMenu(){
          JMenuBar mainMenuBar = new JMenuBar();  //notice - used JMenuBar
          setJMenuBar(mainMenuBar);
          JMenu windowMenu = new JMenu("Window");
          windowMenu.setMnemonic('w');
          mainMenuBar.add(windowMenu);
          newRental = new JMenuItem("New Rental");
          newRental.setAccelerator(KeyStroke.getKeyStroke(KeyEvent.VK_N, ActionEvent.CTRL_MASK));
          newRental.addActionListener(new ActionListener(){
               public void actionPerformed(ActionEvent e){
                    new Rental();
                    one = true;
                    if(!one)
                         new ExistingRentals();
          existingRental = new JMenuItem("Existing Rentals");
          existingRental.setAccelerator(KeyStroke.getKeyStroke(KeyEvent.VK_E, ActionEvent.CTRL_MASK));
          existingRental.addActionListener(new ActionListener(){
               public void actionPerformed(ActionEvent e){
                    new ExistingRentals();
                    one = true;
                    if(!one)
                         new Rental();
          windowMenu.add(newRental);
          windowMenu.add(existingRental);
}JDialog two
import javax.swing.*;]
import java.awt.*;
public class ExistingRentals extends JDialog
     private JList list;
     private JScrollBar scrollHorizontal;
     public ExistingRentals()
          existingRentalAgreement();
          setTitle("Rental List");
          setSize(200, 500);
          setVisible(true);
          setLocationRelativeTo(null);
     public void existingRentalAgreement()
          Container container = getContentPane();
          container.setLayout(new BorderLayout());
          list = new JList();
          scrollHorizontal = new JScrollBar(JScrollBar.HORIZONTAL);
          add(scrollHorizontal, BorderLayout.SOUTH);
          scrollHorizontal.add(list);
}

Answer 1

What if you made your jdialog modal. this can be done by passing a boolean parameter set to "true" to the JDialog super constructor. Here is what I mean with some other minor changes:
ExistingRentals class ----------------------------------------
import javax.swing.*;
import java.awt.*;
public class ExistingRentals extends JDialog
    private JList list;
    private JScrollBar scrollHorizontal;
    public ExistingRentals(JFrame parent, String title)
        super(parent, true); // true here makes dialog modal.[captain.obvious]false does the opposite[/captain.obvious]
        existingRentalAgreement();
        setTitle(title);
        setSize(200, 500);
        setVisible(true);
        setLocationRelativeTo(null);
    public void existingRentalAgreement()
        Container container = getContentPane();
        container.setLayout(new BorderLayout());
        list = new JList();
        scrollHorizontal = new JScrollBar(JScrollBar.HORIZONTAL);
        add(scrollHorizontal, BorderLayout.SOUTH);
        scrollHorizontal.add(list);
import javax.swing.*;
import java.awt.event.*;
public class Data extends JFrame
    JMenuItem existingRental;
    JMenuItem newRental;
    boolean one = true;
    public Data() {
        createMainMenu();
        setSize(350, 100);
        setVisible(true);
        setLocationRelativeTo(null);
        setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
    public static void main(String[] args)
        new Data();
    private void createMainMenu()
        JMenuBar mainMenuBar = new JMenuBar(); // notice - used JMenuBar
        setJMenuBar(mainMenuBar);
        JMenu windowMenu = new JMenu("Window");
        windowMenu.setMnemonic('w');
        mainMenuBar.add(windowMenu);
        newRental = new JMenuItem("New Rental");
        newRental.setAccelerator(KeyStroke.getKeyStroke(KeyEvent.VK_N,
                ActionEvent.CTRL_MASK));
        newRental.addActionListener(new ActionListener()
            public void actionPerformed(ActionEvent e)
                newRentalAction(e);
        existingRental = new JMenuItem("Existing Rentals");
        existingRental.setAccelerator(KeyStroke.getKeyStroke(KeyEvent.VK_E,
                ActionEvent.CTRL_MASK));
        existingRental.addActionListener(new ActionListener()
            public void actionPerformed(ActionEvent e)
                existingRentalAction(e);
        windowMenu.add(newRental);
        windowMenu.add(existingRental);
    private void existingRentalAction(ActionEvent e)
        new ExistingRentals(this, "Existing Rental List");
        // one = true;
        // if (!one) new Rental();
    private void newRentalAction(ActionEvent e)
        // one = true;
        // if (!one)
        new ExistingRentals(this, "New Rental List");
        // new Rental();
}