Why is the @FunctionalInterface annotation added to the Comparator interface in Java 8?

Question

I understand that a bunch of body methods have been added using the defaultJava 8 keyword . My question is, where is this annotation useful? I see that only one abstract method can be added with such annotation. But the comparator has two abstract methods:

• int compare(T o1, T o2);
• boolean equals(Object obj);

Also, please explain the use of this annotation? I see that this is a run-time annotation, so what uses it?

Answer 1

From the documentationFunctionalInterface :

, java.lang.Object, , java.lang.Object .

equals java.lang.Object, . compare, FunctionInterface.

Answer 2

, , . @FunctionalInterface , Java , , @FunctionalInterface. , .