A Frame that lets you draw circles with mouse clicks

SavedFrame.java
****************
A Frame that lets you draw circles with mouse clicks 
//**************
import java.awt.*;
import java.awt.event.*;
import java.io.*;

/** A Frame that lets you draw circles with mouse clicks 
 *  and then save the Frame and all circles to disk.
 *
public class SavedFrame extends CloseableFrame
                        implements ActionListener {
  
  /** If a saved version exists, use it. Otherwise create a 
   *  new one.
   */
                          
  public static void main(String[] args) {
    SavedFrame frame;
    File serializeFile = new File(serializeFilename);
    if (serializeFile.exists()) {
      try {
        FileInputStream fileIn = 
          new FileInputStream(serializeFile);
        ObjectInputStream in = new ObjectInputStream(fileIn);
        frame = (SavedFrame)in.readObject();
        frame.setVisible(true);
      } catch(IOException ioe) {
        System.out.println("Error reading file: " + ioe);
      } catch(ClassNotFoundException cnfe) {
        System.out.println("No such class: " + cnfe);
      }
    } else {
      frame = new SavedFrame();
    }
  }

  private static String serializeFilename ="SavedFrame.ser";
  private CirclePanel circlePanel;
  private Button clearButton, saveButton;

  /** Build a frame with CirclePanel and buttons. */
                          
  public SavedFrame() {
    super("SavedFrame");
    setBackground(Color.white);
    setFont(new Font("Serif", Font.BOLD, 18));
    circlePanel = new CirclePanel();
    add("Center", circlePanel);
    Panel buttonPanel = new Panel();
    buttonPanel.setBackground(Color.lightGray);
    clearButton = new Button("Clear");
    saveButton = new Button("Save");
    buttonPanel.add(clearButton);
    buttonPanel.add(saveButton);
    add(buttonPanel, BorderLayout.SOUTH);
    clearButton.addActionListener(this);
    saveButton.addActionListener(this);
    setSize(300, 300);
    setVisible(true);
  }

  /** If "Clear" clicked, delete all existing circles. If "Save"
   *  clicked, save existing frame configuration (size, 
   *  location, circles, etc.) to disk.
   */
                          
  public void actionPerformed(ActionEvent event) {
    if (event.getSource() == clearButton) {
      circlePanel.removeAll();
      circlePanel.repaint();
    } else if (event.getSource() == saveButton) {
      try {
        FileOutputStream fileOut =
          new FileOutputStream("SavedFrame.ser");
        ObjectOutputStream out = 
          new ObjectOutputStream(fileOut);
        out.writeObject(this);
        out.flush();
        out.close();
      } catch(IOException ioe) {
        System.out.println("Error saving frame: " + ioe);
      }
    }
  }
}
****************