Cannot see intermediate steps in animation

I am having trouble showing a simple animation in a Java application. I paint several circles separated by repaint and sleep requests but I only see the last one, not the intermediate ones. The attached code displays a single "circle" at (100,500). When the user clicks on the "Move" button I want it to show circles at (200,500), (300,500), and (400,500), separated by short delays. However I only see the last one. Probably a simple misconception on my part... Thanks.

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

public class SlowExample{

    private Mypanel mypanel;
    private JButton button;

    public static void main(String[] args) {
        javax.swing.SwingUtilities.invokeLater(
          new Runnable() {
            public void run() {
                JFrame frame = new JFrame();
                frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
                SlowExample eg = new SlowExample();
                frame.setContentPane(eg.createContentPane());
                frame.setSize(800, 800);
                frame.setVisible(true);
            }
          }
        );
    }

    public JPanel createContentPane(){
        JPanel contentPane = new JPanel(new BorderLayout()); 
                
        mypanel = new Mypanel();         
        contentPane.add(mypanel, "Center");

        button = new JButton("Move");
        button.addActionListener(new ButtonHandler(mypanel));
        contentPane.add(button, "South");
        
        return contentPane;
    }
} // end of class SlowExample

class ButtonHandler implements ActionListener {
    private Mypanel mypanel;
    public ButtonHandler(Mypanel mypanel) {
        this.mypanel = mypanel;
    }

    public void actionPerformed(ActionEvent e) {    
    	AbstractButton b = (AbstractButton) e.getSource();
        if (b.getText().equals("Move") ) {
            mypanel.move();
        } else 
        	System.err.println("Unknown source "+b.getText());
    }
} // end of ButtonHandler

class Mypanel extends JPanel{
    private Point p = new Point(100,500);

    public void paintComponent(Graphics g) { 
        super.paintComponent(g);
        int height = getSize().height;
        g.setColor(Color.red);
        g.fillOval(p.x-2, (height - p.y)-2, 8, 8);
    }

    public void move() {
    	p = new Point(200,500);
        repaint();
        try{Thread.sleep(500);} catch (InterruptedException e){};
    	p = new Point(300,500);
        repaint();
        try{Thread.sleep(500);} catch (InterruptedException e){};
        p = new Point(400,500);
        repaint();
    }     
} // end of Mypanel

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