It will cover most topics. Although there are topics like threads for example that go beyond the scope of the exam. Just skip over those. Read the sections towards the end to get a feel for the later objectives but don't worry about the code needed to make it work just understand what the peices of J2EE do.
Do take some time to read up on the materials posted at HFO website, they helps. In addition, you'll need to know your UML & OO concepts well (the diagrams, how they map to codes).
Not to worry too much about digesting all the stuffs in HFJ. I did read through some chapters of it, but thats for another purpose, don't really feel that it is necessary to read HJF to pass the exams.
If you'd done some coding before, it helps. Do read up on the String API.
Overall the questions are pretty well spread across the various sections, so don't focus too much on a particular topic.
If you'd just graduated or would be graduating soon, with your OO & UML knowledge fresh in mind, together with some basic Java programming knowledge & high level understanding of J2SE, J2EE, J2ME & Web Services, it won't be too tough to pass.