Displaying progress with JTextArea

Question

Hi,
As newbie, I'm trying to test a concept to see if I can get the new data be appended and displayed immediately in a JTextArea. I wrote a little application that display the number as it loops through in actionPermformed interface. I put a short pause so I can see the number being refreshed into JtextArea. However, what I get is the application process all the loop and repaint the text area with all numbers. As a result, I don't the get progressing paint effect as the application loop through in for loop. What method I should use to achieve this effect? Here is the code I use.
import javax.swing.*;
import java.awt.*;
import java.awt.event.*;
public class Loop extends JFrame implements ActionListener{
      JTextArea taNum = null;
      JButton btnLoop = null;
      JTextField tfNum = null;
      JScrollPane jspNum= null;
      public Loop (){
        setSize (100,200);
        setLocationRelativeTo(null);
        Container pane = getContentPane();
        pane.setLayout (new GridBagLayout());
        GridBagConstraints c = new GridBagConstraints();
        c.anchor = GridBagConstraints.WEST;
        tfNum = new JTextField(10);
        c.gridx=0;
        c.gridy=0;
        pane.add(tfNum,c);
        btnLoop = new JButton ("Loop");
        btnLoop.addActionListener(this);
        c.gridx=1;
        c.gridy=0;
        pane.add(btnLoop,c);
        taNum = new JTextArea("Start",5,20);
        jspNum = new JScrollPane(taNum);
        c.gridx=0;
        c.gridy=2;
        c.gridwidth=2;
        c.gridheight=2;
        c.ipady=20;
        pane.add(jspNum,c);
        pack();
        setVisible(true);           
      public void actionPerformed (ActionEvent e){
       try{ 
         for (int i =0;i<Integer.parseInt(tfNum.getText());i++){
           taNum.append(Integer.toString(i)+'\n');
           taNum.setCaretPosition(taNum.getDocument().getLength());
           repaint();
           Thread.sleep(500);
        } catch (InterruptedException ex){
          ex.printStackTrace();
      public static void main (String [] argv){
          Loop l = new Loop();
/*************************************/Thank in advance.
Kim
Edited by: kimtitu on Oct 1, 2010 2:03 PM

Answer 1

1) Read the "Welcome to the new home" posting at the top of the forum for information on the proper way to add code to a posting
2) Swing related questions should be posted in the Swing forum which is found under "Java Desktop" from the forums home page.
3) Read the section from the Swing tutorial on [url http://download.oracle.com/javase/tutorial/uiswing/concurrency/index.html]Concurrency for more information about why it doesn't work and for one possible solution.