Whizlabs SCJP question topics vs. Exam Topics detailed in the McGraw Hill SCJP 6 Book

I have been studying for the SCJP 6 for the past months now.

I have read the McGraw Hill SCJP book inside and out.
I have also begun using the test exam package offered by whizlabs.

Very often I find that the McGraw Hill book will explicitly state subtopics that will and will not be on the exam.
For example: API details, regarding methods of Collections, IO classes.

For one, they explicitly state for the Matcher class, "replace operations are not on the exam." (p.500)
Also, the API topics covered for File are limited to 8 methods and 3 constructors (see p. 450).

However the whizlab exams feature questions that, for example,
contain replace methods or contain additional methods and constructors for File.
In addition, they often refer to some more exotic collection types.

My question therefore is: who is the undisputed source what's on the exam and not?

Well the most reliable source for the exam is the SCJP objectives. Whizlabs has many questions which are not on the objectives. Maybe they added those questions to make the mock exams more tough. But recently some topics (like serialization) were removed from the SCJP objectives. The McGraw Hill book is a little old so it has those topics in it. So please refer to the objectives on Oracle's site so that you know which topics to study which not...

Cheers, thanks for the reply.

I just read
a posting from a recent test taker that said Serialization questions should not have been on the test but where (4 of them). I also noted that Serialization is in fact not explicitly mentioned in the current Sun syllabus.

Additionally, it did not seem to specify which collections are covered.

p.s.
Just a general question about serialization and its use in the wide world: is it not as widely used, hence its exclusion from the
Sun syllabus?

Find
Oracle's Sun SJCP 6 Syllabus
here.

Just a general question about serialization and its use in the wide world: is it not as widely used, hence its exclusion from the
Sun syllabus?

Serialization is indeed widely used. As to why it is being excluded I do not know.

By the way, my definition of widely used is 'Used in an application every now and then'. It is certainly a useful feature to understand and remember. It will help you in your job