Progressbar is not showing when downloading file from a given location

Hi all,

I have written a JAVA program for downloading file from given location.
I have used a JProgressBar in GUI for showing downloading status.
But when downloading is starts is not shown it will directly shown at the end of downloading.

I should be displayed at the time of downloading to show the downloading status.

if (panel != null)
		{
			m_progressBar = new JProgressBar();
			m_progressBar.setBounds(0, 0, panel.getWidth(), panel.getHeight());
			m_progressBar.setVisible(true);
			panel.add(m_progressBar);
		}

try
		{

byte[] arrRetVal = null;

File file =
					new File(strSWPath + m_objUpdateUtils.getFileName(fileURL));
			System.out.println("FileName" + file);
			if (file.exists())
				lStartPos = file.length();

while (lStartPos < lFileSize)
			{
				oFileOStream = new FileOutputStream(file, true);
				nlength = lFileSize - lStartPos;
				if (nlength < m_lNoOfBytesToRead)
				{
					m_lNoOfBytesToRead = nlength;
				}

arrRetVal =m_objConnectionUtil.download(fileURL, (int) lStartPos,
					 (int) m_lNoOfBytesToRead);                               
                                    //actual downloading is done here, after successful downloading 
                                   //it will return true boolean value else false.

lStartPos += m_lNoOfBytesToRead;
				oFileOStream.write(arrRetVal);
				bDownload = true;
				iPer = (float) ((float) lStartPos / (float) lFileSize) * 100;
				j = (int) iPer;
				System.out.println("StartPos :: " + lStartPos + "   FileSize :: "
						+ lFileSize);
				if (panel != null)
					m_progressBar.setValue(j);

oFileOStream.close();
			}

this is my code.
Please tell me that how I can see progressBar showing downloading status.
If you have any solution alternate solution then please tell me with sample code
or mark it in the above code, So that it will be easy for me to understand.

Thanks in advance & please reply soon,
byt tc

Please read these two pages:
http://java.sun.com/products/jfc/tsc/articles/threads/threads1.html
http://faq.javaranch.com/java/JProgressBarDoesntUpdate