code: public static String stringToString(String dateString, String desfmt) {
          // ISO_DATE_FORMAT = "yyyyMMdd";
          if (dateString.trim().length() == 8) {
              return stringToString(dateString, ISO_DATE_FORMAT, desfmt);
          } else if (dateString.trim().length() == 10) {
              // ISO_EXPANDED_DATE_FORMAT = "yyyy-MM-dd";
              return stringToString(dateString, ISO_EXPANDED_DATE_FORMAT, desfmt);
          } else if (dateString.trim().length() == 19) {
              // DATETIME_PATTERN = "yyyy-MM-dd hh:mm:ss";
              return stringToString(dateString.substring(0, 10),
                      ISO_EXPANDED_DATE_FORMAT, desfmt);
          } else if (dateString.trim().length() == 11) {
              // CHINESE_EXPANDED_DATE_FORMAT = "yyyy年MM月dd日";
              return stringToString(dateString, CHINESE_EXPANDED_DATE_FORMAT,
                      desfmt);
          }
          return null;
      }
docs: 日期字符串格式转换
  
  @param dateString
  日期字符串
  @param desfmt
  目标日期格式
  @return