code: private void addType(Type t) {
          String signature = t.getSignature();
          if (signature.startsWith(Values.SIG_QUALIFIED_CLASS_PREFIX)) {
              refClasses.add(SignatureUtils.trimSignature(signature));
          }
      }
docs: add the type string represented by the type to the refClasses set if it is a reference
  
  @param t
  the type to add