code: public boolean considerAsAddDirective(String suri) {
          String u = suri.trim();
          if(u.length()==0) {
              // empty string: consider a mistake
              return false; 
          }
          if(u.indexOf("(")>0) {
              // formal SURT prefix; toLowerCase just in case
              add(u.toLowerCase());
          } else {
              // hostname/normal form URI from which 
              // to deduce SURT prefix
              addFromPlain(u);
          }
          return true;
         
      }
docs: Interpret the given SURT/URI/host as a directive, returning true
  if it was meaningful.
  
  @param suri potential directive
  @return boolean true if applied as directive, false otherwise