Java代码优化：简化Excel导入逻辑并提升性能

{"title":"帮我优化以下代码，并解释为什么这么修改：\n public AjaxResult importData(MultipartFile file, boolean updateSupport) throws Exception {\n Workbook workbook = null;\n InputStream inputStream = file.getInputStream();\n String fileExtension = getFileExtension(Objects.requireNonNull(file.getOriginalFilename()));\n //根据文件类型进行区分\n if (fileExtension.equals("xlsx")) {\n workbook = new XSSFWorkbook(inputStream);\n } else if (fileExtension.equals("xls")) {\n workbook = new HSSFWorkbook(inputStream);\n }\n\n String sheetName = "a-HKG BW WHSE-in bound"; // 导入信息的工作表名称\n Sheet sheet = null;\n if (workbook != null) {\n sheet = workbook.getSheet(sheetName);\n }\n if (sheet == null) {\n throw new IllegalArgumentException("Sheet with name " + sheetName + " does not exist");\n }\n InputStream getSheetInputStream = workbookToInputStream(sheet.getWorkbook());\n ExcelUtil util = new ExcelUtil<>(AHkgBwWhseInBound.class);\n List dataManagementList = util.importExcel(getSheetInputStream, 1);\n String operName = ShiroUtils.getSysUser().getLoginName();\n String message = aHkgBwWhseInBoundService.importData(dataManagementList, updateSupport, operName);\n return AjaxResult.success(message);\n }\n\n private static String getFileExtension(String fileName) {\n if (fileName.lastIndexOf(".") != -1 && fileName.lastIndexOf(".") != 0) {\n return fileName.substring(fileName.lastIndexOf(".") + 1);\n } else {\n return "";\n }\n }\n\n private static InputStream workbookToInputStream(Workbook workbook) throws IOException {\n // 创建临时的OutputStream\n ByteArrayOutputStream byteArrayOutputStream = new ByteArrayOutputStream();\n workbook.write(byteArrayOutputStream);\n // 将ByteArrayOutputStream转换为InputStream\n InputStream inputStream = new ByteArrayInputStream(byteArrayOutputStream.toByteArray());\n // 关闭临时的OutputStream\n byteArrayOutputStream.close();\n return inputStream;\n }\n内容：修改后的代码如下：\n\npublic AjaxResult importData(MultipartFile file, boolean updateSupport) throws Exception {\n Workbook workbook = null;\n InputStream inputStream = file.getInputStream();\n String fileExtension = getFileExtension(Objects.requireNonNull(file.getOriginalFilename()));\n // 根据文件类型进行区分\n if (fileExtension.equals("xlsx")) {\n workbook = new XSSFWorkbook(inputStream);\n } else if (fileExtension.equals("xls")) {\n workbook = new HSSFWorkbook(inputStream);\n }\n\n String sheetName = "a-HKG BW WHSE-in bound"; // 导入信息的工作表名称\n Sheet sheet = workbook.getSheet(sheetName);\n if (sheet == null) {\n throw new IllegalArgumentException("Sheet with name " + sheetName + " does not exist");\n }\n InputStream getSheetInputStream = workbookToInputStream(workbook);\n ExcelUtil util = new ExcelUtil<>(AHkgBwWhseInBound.class);\n List dataManagementList = util.importExcel(getSheetInputStream, 1);\n String operName = ShiroUtils.getSysUser().getLoginName();\n String message = aHkgBwWhseInBoundService.importData(dataManagementList, updateSupport, operName);\n return AjaxResult.success(message);\n}\n\nprivate static String getFileExtension(String fileName) {\n int dotIndex = fileName.lastIndexOf(".");\n if (dotIndex != -1 && dotIndex != 0) {\n return fileName.substring(dotIndex + 1);\n } else {\n return "";\n }\n}\n\nprivate static InputStream workbookToInputStream(Workbook workbook) throws IOException {\n ByteArrayOutputStream byteArrayOutputStream = new ByteArrayOutputStream();\n workbook.write(byteArrayOutputStream);\n return new ByteArrayInputStream(byteArrayOutputStream.toByteArray());\n}\n\n修改解释：\n1. 简化了获取文件扩展名的逻辑，使用了更直观的方式。\n2. 移除了对空指针的判断，使用了Objects.requireNonNull确保file.getOriginalFilename()不为null。\n3. 删除了对workbook是否为null的判断，因为如果文件类型不支持，workbook会为null，后续的操作会抛出异常。\n4. 简化了获取sheet的逻辑，直接使用workbook.getSheet(sheetName)获取指定名称的sheet。\n5. 在workbookToInputStream方法中，直接返回创建的ByteArrayInputStream对象，省去了关闭ByteArrayOutputStream的步骤。