code: public static String convertUpperToCamelCase(String _str) {
          if (_str == null || isBlank(_str)) {
              return _str;
          } else if (!_str.contains("_")) {
              return (_str.charAt(0) + "").toUpperCase() + _str.substring(1);
          }
  
          StringBuffer sb = new StringBuffer(String.valueOf(_str.charAt(0)).toUpperCase());
          for (int i = 1; i < _str.length(); i++) {
              char c = _str.charAt(i);
              if (c == '_') {
                  i++; // get next character and convert to upper case
                  c = String.valueOf(_str.charAt(i)).toUpperCase().charAt(0);
              } else {
                  c = String.valueOf(c).toLowerCase().charAt(0);
              }
              sb.append(c);
          }
          return sb.toString();
      }
docs: Tries to convert upper-case string to camel-case.
  The given string will be analyzed and all string parts preceded by an underline character will be
  converted to upper-case, all other following characters to lower-case.
  @param _str string to convert
  @return converted string or original string if there was nothing to do