Java SE (Java Platform, Standard Edition)

Hi! I'm very new to this so I have some noobish question.

I want to create a simple GUI with counter going from 10 to 0 and showing that on JLabel not in program output.I'm not sure if that is possible, but here is my code:

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


public class Test extends JFrame
{
	private JLabel peynJl = new JLabel("Countdown ",JLabel.CENTER);

	private JButton jbOK = new JButton("START");
	
	
	public static void main(String [] args)
	{
	  new	Test();
	}//end of main
	
	public Test()
	{
		setTitle("Countdown");
		
		JPanel jp1 = new JPanel();
		
		jp1.add(peynJl);
		
		
		add(jp1, BorderLayout.CENTER);
		
		JPanel jp2 = new JPanel();
		
		jp2.add(jbOK);
		
		add(jp2, BorderLayout.SOUTH);
		setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
		pack();
		setLocationRelativeTo(null);
		setVisible(true);
		
		addWindowListener(new WindowAdapter() {
					public void windowClosing(WindowEvent we)
					{
						dispose();	
					}
			});
		
		jbOK.addActionListener(new ActionListener() {
				
				public void actionPerformed(ActionEvent ae)
				{
					int i;
					
					for( i=10;i>0;i--)
					{
						peynJl.setText(""+i);

						try
						{
							Thread.sleep(1000);
						}//end of try
						catch(Exception e)
						{
							System.out.println("Sleep error!");
							System.exit(0);
						}//end of catch
							
					}//end of for loop
					
				
						if(i==0)
						{
							JOptionPane.showMessageDialog(null,"Out of time","Counter Reached 0!",JOptionPane.INFORMATION_MESSAGE);
						}
				}//end of actionPerformed
	});//end of new ActionListener

		
	}//enf of constructor
}//end of class

What happens is, this for loop works,I checked, if I set System.out.println(""+i); in the foor loop it will print out every step normally "10,9,8,7..." and with JLabel I don't see that"update" (10,9,8,7..) ,I just get last number set to JLabel (1) after program exits from the for loop.

I apologize if I'm doing some begginers mistake but I would appriciate your help very much.

Thank you in advance.

Toni