下面的程序，显示一个按钮和一个标签。每次点击按钮时，标签都将更新。
package hustspy; import Javax.swing.*; import java.awt.*; import java.awt.event.*; public class hello implements ActionListener { private static String labelPrefix = "Number of button clicks: "; private int numClicks = 0; final JLabel label = new JLabel(labelPrefix + "0 "); //Specify the look and feel to use. Valid values: //null (use the default), "Metal", "System", "Motif", "GTK+" final static String LOOKANDFEEL = "System"; public Component createComponents() { JButton button = new JButton("I'm a Swing button!"); button.setMnemonic(KeyEvent.VK_I); button.addActionListener(this); label.setLabelFor(button); /* * An easy way to put space between a top-level container * and its contents is to put the contents in a JPanel * that has an "empty" border. */ JPanel pane = new JPanel(new GridLayout(0, 1)); pane.add(button); pane.add(label); pane.setBorder(BorderFactory.createEmptyBorder( 30, //top 30, //left 10, //bottom 30) //right ); return pane; } public void actionPerformed(ActionEvent e) { numClicks++; label.setText(labelPrefix + numClicks); } private static void initLookAndFeel() { String lookAndFeel = null; if (LOOKANDFEEL != null) { if (LOOKANDFEEL.equals("Metal")) { lookAndFeel = UIManager.getCrossPlatformLookAndFeelClassName(); } else if (LOOKANDFEEL.equals("System")) { lookAndFeel = UIManager.getSystemLookAndFeelClassName(); } else if (LOOKANDFEEL.equals("Motif")) { lookAndFeel = "com.sun.java.swing.plaf.motif.MotifLookAndFeel"; } else if (LOOKANDFEEL.equals("GTK+")) { //new in 1.4.2 lookAndFeel = "com.sun.java.swing.plaf.gtk.GTKLookAndFeel"; } else { System.err.println("Unexpected value of LOOKANDFEEL specified: " + LOOKANDFEEL); lookAndFeel = UIManager.getCrossPlatformLookAndFeelClassName(); } try { UIManager.setLookAndFeel(lookAndFeel); } catch (ClassNotFoundException e) { System.err.println("Couldn't find class for specified look and feel:" + lookAndFeel); System.err.println("Did you include the L&F library in the class path?"); System.err.println("Using the default look and feel."); } catch (UnsupportedLookAndFeelException e) { System.err.println("Can't use the specified look and feel (" + lookAndFeel + ") on this platform."); System.err.println("Using the default look and feel."); } catch (Exception e) { System.err.println("Couldn't get specified look and feel (" + lookAndFeel + "), for some reason."); System.err.println("Using the default look and feel."); e.printStackTrace(); } } } /** * Create the GUI and show it. For thread safety, * this method should be invoked from the * event-dispatching thread. */ private static void createAndShowGUI() { //Set the look and feel.---设置外观，可以忽略 initLookAndFeel(); //Make sure we have nice window decorations. //设置为false的话，即为不改变外观 JFrame.setDefaultLookAndFeelDecorated(true); //Create and set up the window. JFrame frame = new JFrame("SwingApplication"); frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE); hello app = new hello(); Component contents = app.createComponents(); frame.getContentPane().add(contents, BorderLayout.CENTER); //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(); } }); } }