code: public static String escapeSpecialChar(String keyword) {
          if (!isEmpty(keyword)) {
              String[] fbsArr = {"\\", "$", "(", ")", "*", "+", ".", "[", "]", "?", "^", "{", "}", "|"};
              for (String key : fbsArr) {
                  if (keyword.contains(key)) {
                      keyword = keyword.replace(key, "\\" + key);
                  }
              }
          }
          return keyword;
      }
docs: escape the regex special character: （$()*+.[]?\^{},|）