I just passed the OCAJP with 82% :-)
I thought the real test was easier than the mock exams. The highest I scored on a mock exam was 77% and I didn't feel very confident.
I studied with the OCA Java 8 SE Study Guide (Sybex). It was a great book. I started learning java six months ago, so I had some basic knowledge but was ignorant of a lot of the details. I failed miserably my first mock exam, but the book explained a lot of the fine detail and little tricks I needed to know to pass.
I used mock exams from Whizlabs and Enthuware. I purchased first from Whizlabs, but let me tell you I am never buying from them again. The English was terrible ("What would contain as the 2nd element of the 'aLsit' after executing the all statements" was an actual question. I can't tell you how many times I've wanted to yell 'DOES NOT COMPILE' at those kind of sentences). And to top it all, a few days before the exam, the Whizlabs site became super slow, and then greeted me with a "no database connection" message. So I went to Enthuware. I like their exams much better and will buy from them again to prepare for the OCP exam.
So. Now, on to the OCP exam. I will plan more time to study this time, though. I studied three weeks for the OCA and it worked out, but it was stressful.