code: public final boolean contains(CharSequence s) {
  
          int cp = getSingleCP(s);
          if (cp < 0) {
              return strings.contains(s.toString());
          } else {
              return contains(cp);
          }
      }
docs: Returns <tt>true</tt> if this set contains the given
  multicharacter string.
  @param s string to be checked for containment
  @return <tt>true</tt> if this set contains the specified string