The BS book only gives 4 functional interfaces to study for 1z0-815 : Predicate, Supplier, Consumer and Comparator. Does it mean other interfaces are not in 1z0-815? The actual syllabus does not mention any of them. So a little confused here
As far as stream APIs are concerned, I'm pretty sure knowledge of the Function interface would be require (and maybe the primitive stream APIs like IntFunction). Other than that you should know the rules regarding the function interfaces. From my experience with certification exams (which is 10 years old at this point), it doesn't force you to memorize a lot of APIs. So there might be no need to memorize stuff like BiFunction etc (I might be wrong). In general if you practice writing a lot of code, you'll not have to memorize any API, they'll come naturally to you.
Souvik : You also have to know Comparator for the 815. Everything else is on the 816. Don't worry. You get to learn a load of functional interfaces including Function for the 816 .
Ankit: Since you took the exam, Oracle split it into two parts. Souvik is asking about the easier part. The exam has also changed significantly. You absolutely have to memorize the functional interface APIs for the 809 and 816 exams. Even with Java 5/6, you had to memorize String/ArrayList API.