This bug has been verified in swing-pre-1.0 and jdk1.1.5 by Patience Chu.

"Hi,

I use Swing's JProgressBar in my MPEG analyzer to display progress
relative to the total size of the MPEG stream. I have a case where
MPEG file is about 50MB. In this case, I set minimum to 0 and maximum
to 50000000. When the progress reaches about 20% progress display
disappears and reappears after another 20%.

I am attaching sample code to reproduce the prblem.

Thanks,
----
Venkat Tipparam
Network Products Group
Sun Microsystems.
###@###.###
(650) 688-9410
"
import java.awt.*;
import java.awt.event.*;
import com.sun.java.swing.*;

public class ProgressBarBug extends JFrame implements ActionListener, Runnable {
    int maxValue;
    JTextField textField;
    JProgressBar progressBar;
    JButton startButton;
    Thread thread;
    boolean stopThread = false;
    
    public ProgressBarBug(int maxValue) {
        this.maxValue = maxValue;
        getContentPane().setLayout(new BoxLayout(getContentPane(), BoxLayout.Y_AXIS));
        textField = new JTextField(10);
        textField.setMaximumSize(textField.getPreferredSize());
        textField.setAlignmentX(LEFT_ALIGNMENT);
        progressBar = new JProgressBar();
        progressBar.setAlignmentX(LEFT_ALIGNMENT);
        progressBar.setMinimum(0);
        progressBar.setMaximum(maxValue);
        progressBar.setValue(0);
        startButton = new JButton("Start");
        startButton.setAlignmentX(LEFT_ALIGNMENT);
        startButton.addActionListener(this);
        getContentPane().add(textField);
        getContentPane().add(progressBar);
        getContentPane().add(startButton);
    }

    public void actionPerformed(ActionEvent e) {
        if (e.getSource() == startButton) {
            if (thread != null) {
                stopThread = true;
                thread = null;
            }
            stopThread = false;
            thread = new Thread(this);
            thread.start();
        }
    }
    
    public void run() {
        int value = 0;
        int inc = maxValue / 1000;
        if (inc <= 0) {
            inc = 1;
        }
System.out.println( "ProgressBar Max = " + progressBar.getMaximum());
        while ((value < progressBar.getMaximum()) && !stopThread) {
            value += inc;
            progressBar.setValue(value);
            textField.setText(String.valueOf(value));
            try {
                Thread.sleep(5);
            } catch (InterruptedException e) {
                //
            }
        }
    }

    public static void main(String[] args) {
      int max = 50000000;
      System.out.println( max ) ;
        if (args.length > 0) {
            max = Integer.parseInt(args[0]);
        }
        ProgressBarBug f = new ProgressBarBug(max);
        f.setSize(200, 100);
        f.show();
    }
}