How to create a new sheet in the existing excel file and write some data

File f= new File(System.getProperty("user.dir")+"\\src\\test\\resources\\Exceldata.xls");		
		HSSFWorkbook workbook = new HSSFWorkbook();			
		HSSFSheet worksheet= workbook.createSheet("Sheet4");		
		HSSFRow row = worksheet.createRow(1);
		HSSFCell cell= row.createCell(1);
		cell.setCellValue("admin");		 
        workbook.write(f);
        workbook.close();