New to Java

Hello,
I dont understand why the window produced by this code can not
be shrunk smaller than the size it starts with. I dont see where a minimum size
is set for the Jframe or the components. Why will this window not shrink smaller
than its start size? You can run the code with web start (link below)... This is the behavior I want for my app ... no resizing under 800x600 , but I can shrink my app to almost nothing :p

http://java.sun.com/docs/books/tutorialJWS/uiswing/layout/example-1dot4/GridBagL
ayoutDemo.jnlp

/*
 * GridBagLayoutDemo.java is a 1.4 application that requires no other files.
*/

import java.awt.*;
import javax.swing.JButton;
import javax.swing.JFrame;

public class GridBagLayoutDemo {
    final static boolean shouldFill = true;
    final static boolean shouldWeightX = true;
    final static boolean RIGHT_TO_LEFT = false;

    public static void addComponentsToPane(Container pane) {
        if (RIGHT_TO_LEFT) {
            pane.setComponentOrientation(ComponentOrientation.RIGHT_TO_LEFT);
        }

        JButton button;
        pane.setLayout(new GridBagLayout());
        GridBagConstraints c = new GridBagConstraints();
        if (shouldFill) {
            //natural height, maximum width
            c.fill = GridBagConstraints.HORIZONTAL;
        }

        button = new JButton("Button 1");
        if (shouldWeightX) {
            c.weightx = 0.5;
        }
        c.gridx = 0;
        c.gridy = 0;
        pane.add(button, c);

        button = new JButton("Button 2");
        c.gridx = 1;
        c.gridy = 0;
        pane.add(button, c);

        button = new JButton("Button 3");
        c.gridx = 2;
        c.gridy = 0;
        pane.add(button, c);

        button = new JButton("Long-Named Button 4");
        c.ipady = 40;      //make this component tall
        c.weightx = 0.0;
        c.gridwidth = 3;
        c.gridx = 0;
        c.gridy = 1;
        pane.add(button, c);

        button = new JButton("5");
        c.ipady = 0;       //reset to default
        c.weighty = 1.0;   //request any extra vertical space
        c.anchor = GridBagConstraints.PAGE_END; //bottom of space
        c.insets = new Insets(10,0,0,0);  //top padding
        c.gridx = 1;       //aligned with button 2
        c.gridwidth = 2;   //2 columns wide
        c.gridy = 2;       //third row
        pane.add(button, c);
    }

    /**
     * Create the GUI and show it.  For thread safety,
     * this method should be invoked from the
     * event-dispatching thread.
     */
    private static void createAndShowGUI() {
        //Make sure we have nice window decorations.
        JFrame.setDefaultLookAndFeelDecorated(true);

        //Create and set up the window.
        JFrame frame = new JFrame("GridBagLayoutDemo");
        frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);

        //Set up the content pane.
        addComponentsToPane(frame.getContentPane());

        //Display the window.
        frame.pack();
        frame.setVisible(true);
    }

    public static void main(String[] args) {
        //Schedule a job for the event-dispatching thread:
        //creating and showing this application's GUI.
        javax.swing.SwingUtilities.invokeLater(new Runnable() {
            public void run() {
                createAndShowGUI();
            }
        });
    }
}