/**
 * @version 1.22 2004-08-01
 * @author Cay Horstmann
 */

import java.awt.*;
import java.awt.event.*;
import java.util.*;
import javax.swing.*;

/**
   This program demonstrates that a thread that 
   runs in parallel with the event dispatch thread
   can cause errors in Swing components.
*/
public class SwingThreadTest
{  
   public static void main(String[] args)
   {  
      SwingThreadFrame frame = new SwingThreadFrame();
      frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
      frame.setVisible(true);
   }
}

/**
   This frame has two buttons to fill a combo box from a
   separate thread. The "Good" button uses the event queue, 
   the "Bad" button modifies the combo box directly.
*/
class SwingThreadFrame extends JFrame
{  
   public SwingThreadFrame()
   {  
      setTitle("SwingThreadTest");

      final JComboBox combo = new JComboBox();
      combo.insertItemAt(new Integer(Integer.MAX_VALUE), 0);
      combo.setPrototypeDisplayValue(combo.getItemAt(0));
      combo.setSelectedIndex(0);

      JPanel panel = new JPanel();

      JButton goodButton = new JButton("Good");
      goodButton.addActionListener(new ActionListener()
         {  
            public void actionPerformed(ActionEvent event)
            {  
               new Thread(new GoodWorkerRunnable(combo)).start();
            }
         });
      panel.add(goodButton);
      JButton badButton = new JButton("Bad");
      badButton.addActionListener(new ActionListener()
         {  
            public void actionPerformed(ActionEvent event)
            {  
               new Thread(new BadWorkerRunnable(combo)).start();
            }
         });
      panel.add(badButton);
      panel.add(combo);
      add(panel);
      pack();
   }
}

/**
   This runnable modifies a combo box by randomly adding
   and removing numbers. This can result in errors because
   the combo box methods are not synchronized and both the worker
   thread and the event dispatch thread access the combo box.
*/  
class BadWorkerRunnable implements Runnable
{  
   public BadWorkerRunnable(JComboBox aCombo)
   {  
      combo = aCombo;
      generator = new Random();
   }

   public void run()
   {  
      try
      {
         while (true)
         {  
            combo.showPopup();
            int i = Math.abs(generator.nextInt());
            if (i % 2 == 0)
               combo.insertItemAt(new Integer(i), 0);
            else if (combo.getItemCount() > 0)
               combo.removeItemAt(i % combo.getItemCount());
            Thread.sleep(1);
         }
      }
      catch (InterruptedException e) {}
   }

   private JComboBox combo;
   private Random generator;
}

/**
   This runnable modifies a combo box by randomly adding
   and removing numbers. In order to ensure that the
   combo box is not corrupted, the editing operations are
   forwarded to the event dispatch thread.
*/  
class GoodWorkerRunnable implements Runnable
{  
   public GoodWorkerRunnable(JComboBox aCombo)
   {  
      combo = aCombo;
      generator = new Random();
   }

   public void run()
   {  
      try
      {
         while (true)
         {  
            EventQueue.invokeLater(new 
               Runnable()
               {  
                  public void run()
                  {  
                     combo.showPopup();
                     int i = Math.abs(generator.nextInt());
                     if (i % 2 == 0)
                        combo.insertItemAt(new Integer(i), 0);
                     else if (combo.getItemCount() > 0)
                        combo.removeItemAt(i % combo.getItemCount());
                  }
               });
            Thread.sleep(1); 
         }
      }
      catch (InterruptedException e) {} 
   }

   private JComboBox combo;
   private Random generator;
}







