Should 'Comparable' be a 'Functional interface'?

Question

The definition of a functional interface is \"A functional interface is an interface that has just one abstract method (aside from the methods of Object ), and thus represen

Answer 1

Well, asides from the discussion how usefull the informative annotation @FunctionalInterface is (and I am happy Java 8 does not require it for lambdas).

Comparable is typically a property of a type and therefore not a good candidate for a functional interface. It is explicitly described as the natural ordering and does not take the two this/that arguments. So this property makes it unlikely any method would operate on a lambda (similliar argument is applicable for nearly all -able interfaces).

So, the collection designers use a second interface for that task: Comparator, and for that a lambda implementing it is a very natural choice.