java poi 导出带下拉的excel

public  ArrayList<String> daochu() throws IOException, ClassNotFoundException{
        //初始一个workbook
        HSSFWorkbook workbook = new HSSFWorkbook();
        //创建一个sheet
        HSSFSheet sheet = workbook.createSheet("stustu");
        HSSFRow row = sheet.createRow((int) 0);  
        HSSFCellStyle style = workbook.createCellStyle();  
   style.setAlignment(XSSFCellStyle.ALIGN_CENTER); // 创建一个居中格式  
        HSSFCell cell = row.createCell((short) 0);  
   cell.setCellValue("组织名称");  
   cell.setCellStyle(style);  
   cell = row.createCell((short) 1);  
   cell.setCellValue("组织类别");  
   cell.setCellStyle(style);
   Map<String, String> depttypeMap = sysDicService.queryDicByType("DEPTTYPE");
   ArrayList<String> listo=new ArrayList<String>();
   for(String k : depttypeMap.keySet()){
    System.out.println(k+"----------------------**"+depttypeMap.get(k));
    int x=Integer.valueOf(k);
    listo.add(depttypeMap.get(k));
   }
   String strings[]=new String[listo.size()];
   for(int i=0,j=listo.size();i<j;i++){
   strings[i]=listo.get(i);
   }
        CellRangeAddressList regions = new CellRangeAddressList(1, 10, 4, 4);
        DVConstraint constraint = DVConstraint.createExplicitListConstraint(strings);
        //绑定
        HSSFDataValidation dataValidation = new HSSFDataValidation(regions, constraint);
        sheet.addValidationData(dataValidation);
        FileOutputStream fout = new FileOutputStream("E:/students.xlsx");  
        workbook.write(fout);  
        fout.close(); 
      
        ArrayList<String> list1 = new ArrayList<String>();
   list1.add("E:/students.xlsx");
return list1;


  }