MultipartHttpServletRequest multipartRequest = (MultipartHttpServletRequest) request;MultipartFile multipartFile = multipartRequest.getFile("file");HSSFWorkbook wb = new HSSFWorkbook(multipartFile.getInputStream());HSSFSheet sheet = wb.getSheetAt(0);int num = sheet.getPhysicalNumberOfRows();num獲得的結果 ，如果我清除了內容 它還一直保持著結果記錄，怎么解決這個問題 ，謝謝