Exit regular expression from search bar

Question

We use Regex to match text, for example, follow

       String  str =".*" + s + ".*";

here - s user enters text

  if(stringtext.matches(str .toLowerCase())){
           return true;
   }

The above code works fine when the user enters plain text.
but the user enters any regular expression character, for example, for example. (,},}, ^, $ etc. this gives java.util.regex.PatternSyntaxException: Unclosed group near index 5. (.