import java.awt.BorderLayout;import java.awt.Insets;import java.awt.Toolkit;import java.awt.event.ActionEvent;import java.awt.event.ActionListener;import java.beans.PropertyChangeEvent;import java.beans.PropertyChangeListener;import java.util.Random;import javax.swing.BorderFactory;import javax.swing.JButton;import javax.swing.JComponent;import javax.swing.JFrame;import javax.swing.JPanel;import javax.swing.JProgressBar;import javax.swing.JScrollPane;import javax.swing.JTextArea;import javax.swing.SwingWorker;public class ProgressBar extends JPanel implements ActionListener,        PropertyChangeListener {    private JProgressBar progressBar;    private JButton startButton;    private JTextArea taskOutput;    private Task task;    class Task extends SwingWorker
     
       {        /*         * Main task. Executed in background thread.         */        @Override        public Void doInBackground() {            Random random = new Random();            int progress = 0;            // Initialize progress property.            setProgress(0);            // Sleep for at least one second to simulate "startup".            try {                Thread.sleep(1000 + random.nextInt(2000));            } catch (InterruptedException ignore) {            }            while (progress < 100) {                // Sleep for up to one second.                progress += random.nextInt(10);                setProgress(Math.min(progress, 100));                try {                    Thread.sleep(random.nextInt(1000));                } catch (InterruptedException ignore) {                }                // Make random progress.            }            return null;        }        /*         * Executed in event dispatch thread         */        public void done() {            Toolkit.getDefaultToolkit().beep();            startButton.setEnabled(true);            taskOutput.append("Done!\n");        }    }    public ProgressBar() {        super(new BorderLayout());        // Create the demo's UI.        startButton = new JButton("Start");        startButton.setActionCommand("start");        startButton.addActionListener(this);        progressBar = new JProgressBar(0, 100);        progressBar.setValue(0);        // Call setStringPainted now so that the progress bar height        // stays the same whether or not the string is shown.        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);        add(panel, BorderLayout.PAGE_START);        add(new JScrollPane(taskOutput), BorderLayout.CENTER);        setBorder(BorderFactory.createEmptyBorder(20, 20, 20, 20));    }    /**     * Invoked when the user presses the start button.     */    public void actionPerformed(ActionEvent evt) {        progressBar.setIndeterminate(true);        startButton.setEnabled(false);        // Instances of javax.swing.SwingWorker are not reusuable, so        // we create new instances as needed.        task = new Task();        task.addPropertyChangeListener(this);        task.execute();    }    /**     * Invoked when task's progress property changes.     */    public void propertyChange(PropertyChangeEvent evt) {        if ("progress" == evt.getPropertyName()) {            int progress = (Integer) evt.getNewValue();            progressBar.setIndeterminate(false);            progressBar.setValue(progress);            taskOutput.append(String.format("Completed %d%% of task.\n",                    progress));        }    }    /**     * Create the GUI and show it. As with all GUI code, this must run on the     * event-dispatching thread.     */    private static void createAndShowGUI() {        // Create and set up the window.        JFrame frame = new JFrame("ProgressBar");        frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);        // Create and set up the content pane.        JComponent newContentPane = new ProgressBar();        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();            }        });    }}