code: @SuppressWarnings("unchecked")
      public <TT> StreamEx<TT> select(Class<TT> clazz) {
          return (StreamEx<TT>) filter(clazz::isInstance);
      }
docs: Returns a stream consisting of the elements of this stream which are
  instances of given class.
  
  <p>
  This is an <a href="package-summary.html#StreamOps">intermediate</a>
  operation.
  
  @param <TT> a type of instances to select.
  @param clazz a class which instances should be selected
  @return the new stream