code: public static String underlineToCamel(String param) {
          if (isEmpty(param.trim())) {
              return "";
          }
          StringBuilder sb = new StringBuilder(param);
          Matcher mc = Pattern.compile(UNDERLINE).matcher(param);
          int i = 0;
          while (mc.find()) {
              int position = mc.end() - (i++);
              sb.replace(position - 1, position + 1, sb.substring(position, position + 1).toUpperCase());
          }
          return sb.toString();
      }
docs: convert underline style string to camel style.