Activate Progress Bar outside the main using data claculating in the background - multithreading

Question

i'm trying to activate progress bar that showing the advance of the "for loop" i have while i reading my files and writes them to excel file.
the problam is that the bar don't update to the user until the end of the for loop in each way i tried. what is the right way to do this? is it possible to activate progress bar in the middle of the MyPanel class?
i have the next classes:
Tester(contain the main) , MyPanel , LogFileReader , DefectFileReader.
Tester
public class Tester {
public static void main(String[] args){
JFrame frame = new JFrame("Analayzer GUI");
frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
frame.setSize(450, 300);
frame.setLocationRelativeTo(null);
MyPanel p = new MyPanel();
frame.add(p);
frame.setVisible(true);
}
}
My Panel (only the relevant code)
public class MyActionListener implements ActionListener
{
public void actionPerformed(ActionEvent click)
{
/*...........(code irelevant).......*/
if(click.getSource() == analayze){
Boolean valid = isValidToStart();
if(valid == true){
try{
fos = new FileOutputStream("c:/temp/analayze.xlsx");
if(DFloaded == true){
try {
pbar.repaint();
DF = new File[DFLIST.length];
dfReader = new DefectFileReader[DFLIST.length];
docArray = new Document[DFLIST.length];
for(int i = 0 ; i < DFLIST.length ; i++){
/******* This is where i want to update my bar according to (i/DFList.length) ********/
System.out.println("i'm sending the file down here to parse from file to document");
System.out.println(DFLIST[i].getAbsoluteFile());
DocumentBuilderFactory dbf = DocumentBuilderFactory.newInstance();
DocumentBuilder db = dbf.newDocumentBuilder();
docArray[i] = (Document) db.parse(DFLIST[i]);
docArray[i].getDocumentElement().normalize();
dfReader[i] = new DefectFileReader(DFLIST[i] , docArray[i]);
dfReader[i].getRunsIndex();
totalDuration = sumTimes(dfReader[i].inspectionDuration());
if(i==0){
firstWriteToExcel(dfReader[0], sheet, workbook, fos);
writeToExcel(dfReader[0], sheet, workbook, fos);
}
if(i!=0)
writeToExcel(dfReader[i] , sheet , workbook , fos );
repaint();
if(INPloaded == true){
}
DFLIST[i] = null;
dfReader[i].clearDfReader();
docArray[i] = null;
System.gc();
}
}
catch(Exception e ) {
System.out.println(e);
System.exit(0);
}
}
row = sheet.createRow(rowIndex);
totalDuration = sumTimes("00:00:00");
if(inspectionDuration.getState() == true){
row.createCell(cellIndex - 1).setCellValue(totalDuration);
row.getCell(cellIndex - 1).setCellStyle(csForFirstWrite);
}
((Workbook) workbook).write(fos);
workbook.close();
JOptionPane.showMessageDialog(null, "Your data has been analyze!\n you can find the result in c:\\temp");
System.exit(0);
}catch(Exception e){
e.printStackTrace();
}
}
}