The following application displays a JDialog that is created by the
following constructor:
  new JDialog(new JFrame(), "Modal Dialog", true)

The dialog created by this application is modal on Windows NT, but not
on Solaris.
=========================================================================
/*
 * ModalDialogTest.java
 * JDialog created with modality parameter set to true is not modal on
 * Solaris
 *
 */

import java.awt.BorderLayout;
import java.awt.Color;
import java.awt.GridLayout;
import java.awt.event.*;
import java.awt.swing.*;

public class ModalDialogTest extends JPanel implements ActionListener {
   JDialog dialog = new JDialog(new JFrame(), "Modal Dialog", true);

   public static void main( String[] argv ) {
     new ModalDialogTest();
   }

   public ModalDialogTest() {
      JFrame frame = new JFrame("Modal Dialog Test");
      JPanel controlPanel = new JPanel();
      JPanel infoPanel = new JPanel();
      JButton showButton = new JButton("Show Modal Dialog");
      JButton testButton = new JButton("Test");

      frame.getContentPane().setLayout(new BorderLayout());
      infoPanel.setLayout(new GridLayout(0,1));
      showButton.setOpaque(true);
      showButton.setBackground(Color.yellow);
      testButton.setOpaque(true);
      testButton.setBackground(Color.pink);
      controlPanel.add(showButton);
      controlPanel.add(testButton);
      infoPanel.add(new JLabel("Click the \"Show Modal Dialog\" button to display a modal JDialog."));
      infoPanel.add(new JLabel("Click the \"Test\" button to verify dialog modality."));
      frame.getContentPane().add(BorderLayout.NORTH, controlPanel);
      frame.getContentPane().add(BorderLayout.SOUTH, infoPanel);
      dialog.setSize(200,200);

      showButton.addActionListener(this);
      testButton.addActionListener(this);

      frame.addWindowListener(new WindowAdapter() {
        public void windowClosing(WindowEvent e) {System.exit(0);}
        public void windowClosed(WindowEvent e) {System.exit(0);}
      });

      frame.pack();
      frame.setSize(450, 120);
      frame.setVisible(true);
   }

   public void actionPerformed(ActionEvent evt) {
     String command = evt.getActionCommand();

     if (command == "Show Modal Dialog") {
       System.out.println("*** Invoking JDialog.show() ***");
       dialog.setLocation(200,200);
       dialog.show();
     }
     else if (command == "Test") {
       System.out.println("*** Test ***");
     }
   }

}
=========================================================================