How does Collections.reverseOrder know what type parameter to use while returning Comparator

Question

As per Java API spec, the signature of Collections.reverseOrder is

public static Comparator reverseOrder()

And the example gi

Answer 1

Types in methods calls can be inferred.

Xyz[] a;
Arrays.sort(a, Collections.reverseOrder());

is equivalent to

Xyz[] a;
Arrays.sort(a, Collections.reverseOrder());

From Java SE 7 something similar works for constructors, only you need to use the "diamond 'operator'" (for not very good reasons).

List xyzs = new ArrayList<>();