POI excel rewrite file

Hi,

I would like to write to an existing excel file using POI. I added a clause to check if file doesn't exist, create a new excel, or if exist, create a new worksheet.
when i execute the program, i can the see a new excel file being created. when i execute again, i see the file size increase . but when i open up the excel file, i couldn't see any added changes. after i close the excel file, the file size decrease.

Please help.

try
{
 
String outFilename="workbook.xls";
 
File lFile = new File(outFilename);
// create a new file
 
FileInputStream lFin=null;
POIFSFileSystem fs=null;
HSSFWorkbook wb = null;
HSSFSheet s=null;
HSSFSheet s2=null; 
if (lFile.exists()) 
{
   System.out.println("file");    
      try {
        lFin=new FileInputStream(outFilename);
        fs =new POIFSFileSystem(lFin);
        wb = new HSSFWorkbook(fs);
        s2 = wb.getSheetAt(0);
      }catch (Exception e) 
      {
        e.printStackTrace();
      }
}//if (outF.exists()) 
else
{
 
    System.out.println("no file");
// create a new workbook
wb = new HSSFWorkbook();
}
// create a new sheet
s = wb.createSheet("Sheet4");
 
// declare a row object reference
HSSFRow r = null;
 
// declare a cell object reference
HSSFCell c = null;
short rownum;
 
for (rownum = (short) 0; rownum < 30; rownum++)
{
    // create a row
    r = s.createRow(rownum);
  
    for (short cellnum = (short) 0; cellnum < 10; cellnum += 2)
    {
        // create a numeric cell
        c = r.createCell(cellnum);
        // do some goofy math to demonstrate decimals
        c.setCellValue(rownum * 10000 + cellnum);
    }
}
 
FileOutputStream out = new FileOutputStream(outFilename,true);
wb.write(out);
out.close();
lFin.close(); 
}catch (Exception e)
{
e.printStackTrace ();
}

[ August 12, 2008: Message edited by: zelynn goay ]
[ August 12, 2008: Message edited by: zelynn goay ]

It's probably not a good idea to write to a file while it's still open for reading. Try closing the input file first, and then writing to it.

ok. thanks.