of thepublic methods of java.lang.Object, that also does not count toward the interface's abstract method count since any implementation of the interface will have an implementation from java.lang.Object or elsewhere.

Note that instances of functional interfaces can be created withlambda expressions, method references, or constructor references.

If a type is annotated with this annotation type, compilers arerequired to generate an error message unless:
? The type is an interface type and not an annotation type, enum, or class.
? The annotated type satisfies the requirements of a functional interface.