You can declare that an interface is a functional interface by preceding it with the @FunctionalInterface annotation. The compiler will then ensure that the interface contains ________; otherwise, it'll generate a compilation error.
A) no abstract methods
B) all abstract methods
C) only one abstract method
D) one or more abstract methods.

Question

Quizplus · Accepted Answer

A functional interface should contain only one abstract method. Preceding the interface with @FunctionalInterface annotation ensures that it contains only one abstract method. If the interface contains no abstract methods or more than one abstract method, then the compiler generates a compilation error.

You Can Declare That an Interface Is a Functional Interface