把excel导入的自定义时间改成yyyyMMdd

public static String changeCellToString(XSSFCell cell){
      String result = "";
//     Object value = null;
      DecimalFormat df = new DecimalFormat("#");
      if (null != cell) {
         switch (cell.getCellType()) {
           case HSSFCell.CELL_TYPE_NUMERIC:// 数字类型
               if (HSSFDateUtil.isCellDateFormatted(cell)) {// 处理日期格式、时间格式
                   SimpleDateFormat sdf = null;
                   if (cell.getCellStyle().getDataFormat() == HSSFDataFormat
                           .getBuiltinFormat("h:mm")) {
                       sdf = new SimpleDateFormat("HH:mm");
                   } else {// 日期
                       sdf = new SimpleDateFormat("yyyyMMdd");
                   }
                   Date date = cell.getDateCellValue();
                   result = sdf.format(date);
               } else if (cell.getCellStyle().getDataFormat() == 58) {
                   // 处理自定义日期格式：m月d日(通过判断单元格的格式id解决，id的值是58)
                   SimpleDateFormat sdf = new SimpleDateFormat("yyyyMMdd");
                   double value = cell.getNumericCellValue();
                   Date date = org.apache.poi.ss.usermodel.DateUtil
                           .getJavaDate(value);
                   result = sdf.format(date);
               } else {
                   double value = cell.getNumericCellValue();
                   CellStyle style = cell.getCellStyle();
                   DecimalFormat format = new DecimalFormat();
                   String temp = style.getDataFormatString();
                   // 单元格设置成常规
                   if (temp.equals("General")) {
                       format.applyPattern("#");
                   }
                   result = format.format(value);
               }
               break;
           case HSSFCell.CELL_TYPE_STRING:// String类型
               result = cell.getRichStringCellValue().toString();
               break;
           case HSSFCell.CELL_TYPE_BLANK:
               result = "";
           default:
               result = "";
               break;
           }
      }
      return result;
   }