Why Comparator::reverseOrder does not work with sorted method in a stream?

[Marcelo Canaparro]

I do not get why the static call to the method works and the reference to the method does not. Any ideas?

import java.util.Comparator;
import java.util.stream.Stream;

public class Main {

    public static void main(String[] args) {
        Stream<Integer> stream = Stream.of(2,3,1);
        stream.sorted(Comparator.reverseOrder()).forEach(System.out::println);
        stream.sorted(Comparator::reverseOrder).forEach(System.out::println);
    }
}

[Stephan van Hulst]

Comparator::reverseOrder is not equivalent to Comparator.reverseOrder(). It's equivalent to () -> Comparator.reverseOrder().

Comparator.reverseOrder() returns a Comparator<T>.

Comparator::reverseOrder returns something compatible with Supplier<Comparator<T>>.

[Marcelo Canaparro]

Of course, that is the reason.

Great answer by the way, right to the point. The book gave a two paragraph explanation which I could not make sense of.

[Campbell Ritchie]

Marcelo Canaparro wrote:. . . . The book gave a two paragraph explanation . . .

Which book?

[Marcelo Canaparro]

I am reading the OCP Oracle Certified Professional Java SE 11 Programmer II Study Guide, its awesome but sometimes it makes me confused

[Campbell Ritchie]

Thank you.