import java.awt.*;import java.awt.event.*;import javax.swing.*; public class ProgressBarDemo extends JFrame {    public final static int ONE_SECOND = 1000;    private JProgressBar progressBar;    private Timer timer;    private JButton startButton;    private LongTask task;    private JTextArea taskOutput;    private String newline = "\n";    public ProgressBarDemo() {        super("ProgressBarDemo");        task = new LongTask();        //Create the demo's UI.        startButton = new JButton("Start");        startButton.setActionCommand("start");        startButton.addActionListener(new ButtonListener());        progressBar = new JProgressBar(0, task.getLengthOfTask());        progressBar.setValue(0);        progressBar.setStringPainted(true);        taskOutput = new JTextArea(5, 20);        taskOutput.setMargin(new Insets(5,5,5,5));        taskOutput.setEditable(false);        JPanel panel = new JPanel();        panel.add(startButton);        panel.add(progressBar);        JPanel contentPane = new JPanel();        contentPane.setLayout(new BorderLayout());        contentPane.add(panel, BorderLayout.NORTH);        contentPane.add(new JScrollPane(taskOutput), BorderLayout.CENTER);        contentPane.setBorder(BorderFactory.createEmptyBorder(20, 20, 20, 20));        setContentPane(contentPane);        //Create a timer.        timer = new Timer(ONE_SECOND, new ActionListener() {            public void actionPerformed(ActionEvent evt) {                progressBar.setValue(task.getCurrent());                taskOutput.append(task.getMessage() + newline);                taskOutput.setCaretPosition(                        taskOutput.getDocument().getLength());                if (task.done()) {                    Toolkit.getDefaultToolkit().beep();                    timer.stop();                    startButton.setEnabled(true);                    progressBar.setValue(progressBar.getMinimum());                }            }        });    }    /**     * The actionPerformed method in this class     * is called when the user presses the start button.     */    class ButtonListener implements ActionListener {        public void actionPerformed(ActionEvent evt) {            startButton.setEnabled(false);            task.go();            timer.start();        }    }        public static void main(String[] args) {        JFrame frame = new ProgressBarDemo();        frame.addWindowListener(new WindowAdapter() {            public void windowClosing(WindowEvent e) {                System.exit(0);            }        });        frame.pack();        frame.setVisible(true);    }}