About Question enthuware.ocpjp.v21.2.3352 :

[giginar]

Hello, do we need to know other methods of Comparator interface such as comparing, comparingInt, naturalOrder, reversed, reversedOrder?

[admin]

Yes, at least comparing and reversed also.
But if you are going through the Javadoc for Comparator, take a look at others too, especially the thenComparing type methods.