import java.awt.*;import java.awt.event.*;import javax.swing.*;/* * ComboBoxDemo.java is a 1.4 application that uses these additional files: *   images/Bird.gif *   images/Cat.gif *   images/Dog.gif *   images/Rabbit.gif *   images/Pig.gif */public class ComboBoxDemo extends JPanel                          implements ActionListener {    JLabel picture;    public ComboBoxDemo() {        super(new BorderLayout());        String[] petStrings = { "Bird", "Cat", "Dog", "Rabbit", "Pig" };        //Create the combo box, select the item at index 4.        //Indices start at 0, so 4 specifies the pig.        JComboBox petList = new JComboBox(petStrings);        petList.setSelectedIndex(4);        petList.addActionListener(this);        //Set up the picture.        picture = new JLabel();        picture.setFont(picture.getFont().deriveFont(Font.ITALIC));        picture.setHorizontalAlignment(JLabel.CENTER);        updateLabel(petStrings[petList.getSelectedIndex()]);        picture.setBorder(BorderFactory.createEmptyBorder(10,0,0,0));        //The preferred size is hard-coded to be the width of the        //widest image and the height of the tallest image + the border.        //A real program would compute this.        picture.setPreferredSize(new Dimension(177, 122+10));        //Lay out the demo.        add(petList, BorderLayout.PAGE_START);        add(picture, BorderLayout.PAGE_END);        setBorder(BorderFactory.createEmptyBorder(20,20,20,20));    }    /** Listens to the combo box. */    public void actionPerformed(ActionEvent e) {        JComboBox cb = (JComboBox)e.getSource();        String petName = (String)cb.getSelectedItem();        updateLabel(petName);    }    protected void updateLabel(String name) {        ImageIcon icon = createImageIcon("images/" + name + ".gif");        picture.setIcon(icon);        picture.setToolTipText("A drawing of a " + name.toLowerCase());        if (icon != null) {            picture.setText(null);        } else {            picture.setText("Image not found");        }    }    /** Returns an ImageIcon, or null if the path was invalid. */    protected static ImageIcon createImageIcon(String path) {        java.net.URL imgURL = ComboBoxDemo.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() {        //Make sure we have nice window decorations.        JFrame.setDefaultLookAndFeelDecorated(true);        //Create and set up the window.        JFrame frame = new JFrame("ComboBoxDemo");        frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);        //Create and set up the content pane.        JComponent newContentPane = new ComboBoxDemo();        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();            }        });    }}