code: public static <T extends Comparable<? super T>, A, D> Collector<T, ?, D> maxAll(Collector<T, A, D> downstream) {
          return maxAll(Comparator.<T> naturalOrder(), downstream);
      }
docs: Returns a {@code Collector} which finds all the elements which are equal
  to each other and bigger than any other element according to the natural
  order. The found elements are reduced using the specified downstream
  {@code Collector}.
  
  @param <T> the type of the input elements
  @param <A> the intermediate accumulation type of the downstream collector
  @param <D> the result type of the downstream reduction
  @param downstream a {@code Collector} implementing the downstream
  reduction
  @return a {@code Collector} which finds all the maximal elements.
  @see #maxAll(Comparator, Collector)
  @see #maxAll(Comparator)
  @see #maxAll()