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java swing: previous paintings disappear

Hi,
an oval is created in graphArea (a JPanel) on mouseClicked. However, as soon as the mouse is clicked for the second (n-th) time, the first (previous) oval disappears and another oval appears on the new location. How can i keep the old the new ovals, too?
In general, how can i keep the old painted components and the new ones? (It has probably something to do with the repaint(), but i don't know what...)
A hint?

Code:

import java.awt.*;

import java.awt.event.*;

import javax.swing.*;

import java.awt.Graphics;



public class MainPanel extends JFrame

{    

    /*  To make a local variable available to an  

    *  inner class, just save a copy of the variable as a 

    *  final local variable.

    */

    

    int clickedX;

    int clickedY;

    JPanel graphArea;  

    JPanel outPanel;

    JPanel inPanel;

    

    public MainPanel() 

    {

        //setDefaultCloseOperation(EXIT_ON_CLOSE);

        setSize(new Dimension(800, 600));        

        setLayout(new BorderLayout());

        

        /*  setting up the area of the graph    */

        graphArea=new JPanel()

        {

            public void paintComponent(Graphics g)

            {

                g.drawOval(clickedX,clickedY, 25,25);

                g.drawString("a",clickedX+13, clickedY+13);

            }

        };  

        

        graphArea.addMouseListener(new MouseAdapter()

        {

          public void mouseClicked (MouseEvent e)

          {

                clickedY=e.getY();

                clickedX=e.getX();

                System.out.println("Mouse clicked X: "+clickedX+" Y:"+clickedY);          

                repaint();      

          }

        });

        graphArea.setBorder(BorderFactory.createTitledBorder("graphArea"));

        graphArea.setPreferredSize(new Dimension(640, 340));        

        getContentPane().add(graphArea, BorderLayout.WEST);

        

        /* setting up the area of the outcoming connections */

        outPanel=new JPanel();

        outPanel.setBackground(Color.LIGHT_GRAY);

        addCheckBox(outPanel);

        outPanel.setBorder(BorderFactory.createTitledBorder("Outcoming Connections"));

        outPanel.setPreferredSize(new Dimension(120, 200));        

        getContentPane().add(outPanel,BorderLayout.PAGE_END);

        

        

        /* setting up the area of the incoming connections */

        inPanel=new JPanel();

        inPanel.setBackground(Color.LIGHT_GRAY);

        addCheckBox(inPanel);

        inPanel.setBorder(BorderFactory.createTitledBorder("Incoming Connections"));

        inPanel.setPreferredSize(new Dimension(160, 240));        

        getContentPane().add(inPanel,BorderLayout.LINE_END);

        

        setVisible(true);

    }    

    

    /*  provided, that num is even  */

    void addCheckBox(JPanel pane)

    {

        int j=0;

        for (int i=0; i<4; i++)

        {

            pane.add(new JCheckBox(Integer.toString(++j)));            

            pane.add(new JCheckBox(Integer.toString(++j)));

        }

    }



    public static void main(String[] args)

    {

        new MainPanel();

    }

    

}

Here it is...
Method repaint() clears the background. However, method updateUI() of JPanel, must be implemented on method update() of JComponent, which doesn't clear the background.

Code:

  graphArea.addMouseListener(new MouseAdapter()

        {

          public void mouseClicked (MouseEvent e)

          {

                clickedY=e.getY();

                clickedX=e.getX();

                System.out.println("Mouse clicked X: "+clickedX+" Y:"+clickedY);          

                graphArea.updateUI();      

          }

        });

The only sure way to add multiple items to be displayed - and then to make sure they're all displayed each and every time the panel is refreshed (expose event, minimize/maximize, resize, etc) is:

a) Make a list of your graphics entities (an array, one or another Java container - etc)
b) Iterate through that list in your "paint()" method

I did not understand the whole question, but I wrote this and it will keep the previous Oval thing. Is this what you were looking for?

Code:

import javax.swing.*;

import java.awt.*;

import java.awt.event.*;



public class DrawOval extends JFrame {



    private static int x, y;



    private JPanel pane = new JPanel();



    public DrawOval() {

        setDefaultCloseOperation(EXIT_ON_CLOSE);

        setSize(800, 600);

                

                

        pane.addMouseListener(new MouseAdapter() {

            public void mouseClicked(MouseEvent e) {

                x = e.getX();

                y = e.getY();

                System.out.println(e.toString());

            }

        });

                

        getContentPane().add(pane);

                

        setVisible(true);

                

    }

        

    public static void main(String[] args) {

        new DrawOval();

    }



    public void paint (Graphics g) {

        super.repaint();

        g.setColor(Color.BLACK);

        g.drawOval(x, y, 30, 30);



    }



}

Hi Mega Man X,
you understood right. The repaint() does indirectly exactly what updateUI() and update() does. From the API:

Quote:

If this component is a lightweight component, this method causes a call to this component's paint method as soon as possible. Otherwise, this method causes a call to this component's update method as soon as possible.