Show the most recent image, display only it.

Hi All,
This is a demo program only of my problem. My real
program is too big to be included here.

In this program, given a button panel, a label on a panel,
 a image icon on that label then making a single press of
button b1, gets the image from the url. To see the image
button b2 is pressed. However if I then repeately press
button b2, to show the image, each image is parked along
side of the previous one, or in the next row. Again show
most recent one only, not all the previous ones, showi it
in the location of the first one.

TIA
bH

import java.awt.image.*;
import javax.imageio.*;
import java.io.*;
import java.awt.*;
import java.awt.event.*;
import javax.swing.*;
import java.net.*;

public class GDP extends JFrame
  implements ActionListener {

  private Icon myImage = new ImageIcon();
  private JButton b1 = new JButton("Get Drawing");
  private JButton b2 = new JButton("Drawing is >>>");
  private JButton b3= new JButton("Close");
  private Boolean counterFlag = false;
  private BufferedImage image;
  public static void main(String[] args){
    new GDP ().go();
  }
  void go()
  {
    JPanel labelPanel = new JPanel();
    JPanel btnPanel = new JPanel();
    btnPanel.add(b1);
    b1.addActionListener(this);
    btnPanel.add(b2);
    b2.addActionListener(this);
    btnPanel.add(b3);
    b3.addActionListener(this);

    Container contentPane= getContentPane();
    contentPane.setLayout( new FlowLayout() );
    setSize(350,200);
    contentPane.add(btnPanel );
    contentPane.add(labelPanel);
    this.setResizable(false);
    setVisible(true);
  }

  public void actionPerformed(ActionEvent e) {
    String udp1 = "http://www.extension.iastate.edu/gif/"+
    "Balls/l_green.gif";
    String udp2 = "http://www.extension.iastate.edu/gif/"+
    "Balls/l_red.gif";
    String udp = "";
    if(e.getSource() == b1){
      try {
        if(counterFlag == false){
          udp = udp1;
        }
        else{
          udp = udp2;
        }
        URL url = new URL(udp);
        image = ImageIO.read(url);
        counterFlag = true;
      }
      catch (IOException em) {
        System.out.println("import Data: I/O exception");
      }
      System.out.println
        ("Now press Drawing Is >>> if you want to see it");

    } //end b1
    if(e.getSource() == b2){
      Image img = image ;
      JLabel label = new JLabel(new ImageIcon(img)) ;
      label.setLayout( new GridLayout(0,1) );
      getContentPane().add(label) ;
      setVisible( true );

    } //end b2

    if(e.getSource() == b3){
      System.exit(0);

    } //end b3
  } // action draw picture
}