docs: public static String underScore2CamelCase(String strs) {
  
          if (strs == null || !strs.contains("_")) {
              return strs;
          }
          StringBuilder sb = new StringBuilder("");
          String[] elems = strs.split("_");
          for (int i = 0; i < elems.length; i++) {
              String elem = elems[i].toLowerCase();
              if (i != 0) {
                  char first = elem.toCharArray()[0];
                  sb.append((char) (first - 32)).append(elem.substring(1));
              } else {
                  sb.append(elem);
              }
          }
          return sb.toString();
      }