In Effective Java, in the item "Use bounded wildcards to increase API flexibility", when talking about the usage of PECS (producer-extends, consumer-super), the author mentioned that:
Comparables are always consumers, so you should generally use Comparable<? super T> in preference to Comparable. The same is true of comparators; therefore, you should generally use Comparator<? super T> in preference to Comparator.
It is not clear to me why Comparables and Comparators are considered consumers.
In one of the topic discussing PECS, What is PECS (Producer Extends Consumer Super)?, the consumer is usually referring to a Collection as a parameter for some generic method.
While here Comparable is just an interface.
Can anyone share some insights? Thanks!