Salvar arquivos pelo POI

try {
            InputStream input = te.class.getResourceAsStream( "jesse.xls" );
            POIFSFileSystem fs = new POIFSFileSystem( input );
            HSSFWorkbook wb = new HSSFWorkbook(fs);
            HSSFSheet sheet = wb.getSheetAt(0);
            
            //varre linha a linha da planilha
            Iterator rows = sheet.rowIterator(); 
            while( rows.hasNext() ) {           
                HSSFRow row = (HSSFRow) rows.next();
               
 
                // varre cada celula da linha e imprime seu valor na Tela
                Iterator cells = row.cellIterator();
                while( cells.hasNext() ) {
                    HSSFCell cell = (HSSFCell) cells.next();
                    
                     switch ( cell.getCellType() ) {
                        case HSSFCell.CELL_TYPE_NUMERIC:
                            jTextArea1.setText(jTextArea1.getText()+ "\n" + "Cell #" 
                                    + cell.getCellNum() +"  " +"Row #" + row.getRowNum()+" "
                                    + cell.getNumericCellValue());
                            break;
                        case HSSFCell.CELL_TYPE_STRING: 
                            jTextArea1.setText(jTextArea1.getText()+ "\n" + "Cell #" 
                                    + cell.getCellNum() +"  " +"Row #" + row.getRowNum()+" "
                                    + cell.getRichStringCellValue());
                            cell.setCellValue(867); // aki tento alterar o valor da celula...
                            break;
                        default:
                            System.out.println( "unsuported sell type" );
                            break;

                     }             
                           
                    
                     }
                }
            
 }
                catch ( IOException ex ) { System.exit(0);
            ex.printStackTrace();
        
                }