code: public static String md5(String text) {
          if (text == null) {
              return null;
          }
          if (text.length() == 0) {
              return "";
          }
          try {
              md1.update(text.getBytes("UTF8"));
              return hex(md1.digest());
          } catch (Exception e) {
              e.printStackTrace();
          }
          return null;
      }
docs: Md5加密
  
  @param text
  输入
  @return md5 编码