Excel在office之前和之后的格式不一样，07之前的后缀是.xls，07及07之后.xlsx,针对不同的格式，apache提供了不同的类来操作：HSSF来操作07之前的，XSSF来操作07及07之后。
在pom.xml中要对包进行依赖，一定要两个包都要引入，因为这两个包有依赖关系：
<dependency><groupId>org.apache.poi</groupId><artifactId>poi</artifactId><version>4.0.1</version></dependency><dependency><groupId>org.apache.poi</groupId><artifactId>poi-ooxml</artifactId><version>4.0.1</version></dependency>
对07之前版本的Excel，操作如下：
//textlists存放列表中要展示的字符串String[] textlists = {"doudou1", "doudou2", "doudou3"};//生成一个工作簿对象HSSFWorkbook workbook = new HSSFWorkbook();//生成一个名称为Info的表单HSSFSheet sheet = workbook.createSheet("Info");//设置下拉列表作用的单元格(firstrow, lastrow, firstcol, lastcol)CellRangeAddressList regions = new CellRangeAddressList(1, 100, 0, 0);//生成并设置数据有效性验证DVConstraint constraint = DVConstraint.createExplicitListConstraint(textlists);HSSFDataValidation data_validation_list = new HSSFDataValidation(regions, constraint);//将有效性验证添加到表单sheet.addValidationData(data_validation_list);try{OutputStream os = new FileOutputStream("D:\\doudou.xls");workbook.write(os); //将工作簿内容输出到Excel文件中os.close();workbook.close();} catch (Exception e){e.printStackTrace();}
对Excel07及之后的文件，使用的类不同，思想类似：
XSSFWorkbook workbook = new XSSFWorkbook();XSSFSheet sheet = workbook.createSheet("下拉列表测试");String[] datas = new String[]{"维持", "恢复", "调整"};XSSFDataValidationHelper dvHelper = new XSSFDataValidationHelper(sheet);XSSFDataValidationConstraint dvConstraint = (XSSFDataValidationConstraint)dvHelper.createExplicitListConstraint(datas);CellRangeAddressList addressList = null;XSSFDataValidation validation = null;addressList = new CellRangeAddressList(1,100,0,0);validation = (XSSFDataValidation)dvHelper.createValidation(dvConstraint, addressList);//这两行设置单元格只能是列表中的内容，否则报错validation.setSuppressDropDownArrow(true);validation.setShowErrorBox(true); sheet.addValidationData(validation);try{OutputStream os = new FileOutputStream("D:\\dou.xlsx");workbook.write(os);os.close();workbook.close();} catch (Exception e){e.printStackTrace();}
对以上demo做以记录，便于回顾
