Java: CheckBoxDemo

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

/*
* CheckBoxDemo.java requires 16 image files in the public/images/article/geek
* directory:
* geek-----.gif, geek-c---.gif, geek--g--.gif, geek---h-.gif, geek----t.gif,
* geek-cg--.gif, ..., geek-cght.gif.
*/
public class CheckBoxDemo extends JPanel
                          implements ItemListener {
    JCheckBox chinButton;
    JCheckBox glassesButton;
    JCheckBox hairButton;
    JCheckBox teethButton;

    /*
     * Four accessory choices provide for 16 different
     * combinations. The image for each combination is
     * contained in a separate image file whose name indicates
     * the accessories. The filenames are "geek-XXXX.gif"
     * where XXXX can be one of the following 16 choices.
     * The "choices" StringBuffer contains the string that
     * indicates the current selection and is used to generate
     * the file name of the image to display.

       ----             //zero accessories

       c---             //one accessory
       -g--
       --h-
       ---t

       cg--             //two accessories
       c-h-
       c--t
       -gh-
       -g-t
       --ht

       -ght             //three accessories
       c-ht
       cg-t
       cgh-

       cght             //all accessories
     */

    StringBuffer choices;
    JLabel pictureLabel;

    public CheckBoxDemo() {
        super(new BorderLayout());

        //Create the check boxes.
        chinButton = new JCheckBox("Chin");
        chinButton.setMnemonic(KeyEvent.VK_C);
        chinButton.setSelected(true);

        glassesButton = new JCheckBox("Glasses");
        glassesButton.setMnemonic(KeyEvent.VK_G);
        glassesButton.setSelected(true);

        hairButton = new JCheckBox("Hair");
        hairButton.setMnemonic(KeyEvent.VK_H);
        hairButton.setSelected(true);

        teethButton = new JCheckBox("Teeth");
        teethButton.setMnemonic(KeyEvent.VK_T);
        teethButton.setSelected(true);

        //Register a listener for the check boxes.
        chinButton.addItemListener(this);
        glassesButton.addItemListener(this);
        hairButton.addItemListener(this);
        teethButton.addItemListener(this);

        //Indicates what's on the geek.
        choices = new StringBuffer("cght");

        //Set up the picture label
        pictureLabel = new JLabel();
        pictureLabel.setFont(pictureLabel.getFont().deriveFont(Font.ITALIC));
        updatePicture();

        //Put the check boxes in a column in a panel
        JPanel checkPanel = new JPanel(new GridLayout(0, 1));
        checkPanel.add(chinButton);
        checkPanel.add(glassesButton);
        checkPanel.add(hairButton);
        checkPanel.add(teethButton);

        add(checkPanel, BorderLayout.LINE_START);
        add(pictureLabel, BorderLayout.CENTER);
        setBorder(BorderFactory.createEmptyBorder(20,20,20,20));
    }

    /** Listens to the check boxes. */
    public void itemStateChanged(ItemEvent e) {
        int index = 0;
        char c = '-';
        Object source = e.getItemSelectable();

        if (source == chinButton) {
            index = 0;
            c = 'c';
        } else if (source == glassesButton) {
            index = 1;
            c = 'g';
        } else if (source == hairButton) {
            index = 2;
            c = 'h';
        } else if (source == teethButton) {
            index = 3;
            c = 't';
        }

        //Now that we know which button was pushed, find out
        //whether it was selected or deselected.
        if (e.getStateChange() == ItemEvent.DESELECTED) {
            c = '-';
        }

        //Apply the change to the string.
        choices.setCharAt(index, c);

        updatePicture();
    }

    protected void updatePicture() {
        //Get the icon corresponding to the image.
        ImageIcon icon = createImageIcon(
                                    "public/images/article/geek/geek-"
                                    + choices.toString()
                                    + ".gif");
        pictureLabel.setIcon(icon);
        pictureLabel.setToolTipText(choices.toString());
        if (icon == null) {
            pictureLabel.setText("Missing Image");
        } else {
            pictureLabel.setText(null);
        }
    }

    /** Returns an ImageIcon, or null if the path was invalid. */
    protected static ImageIcon createImageIcon(String path) {
        java.net.URL imgURL = CheckBoxDemo.class.getResource(path);
        if (imgURL != null) {
            return new ImageIcon(imgURL);
        } else {
            System.err.println("Couldn't find file: " + path);
            return null;
        }
    }

    /**
     * Create the GUI and show it.  For thread safety,
     * this method should be invoked from the
     * event-dispatching thread.
     */
    private static void createAndShowGUI() {
        //Create and set up the window.
        JFrame frame = new JFrame("CheckBoxDemo");
        frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);

        //Create and set up the content pane.
        JComponent newContentPane = new CheckBoxDemo();
        newContentPane.setOpaque(true); //content panes must be opaque
        frame.setContentPane(newContentPane);

        //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();
            }
        });
    }
}