I've passed the exam this week. Since five years I'm a Java programmer and this was my first exam. I studied for about three months, but not to achieve some certification. It's more about to get a deeper knowledge of the stuff I'm doing everyday and how it works ;-)
So I red OCA Java 8 SE Programmer I Exam Guide from Kathy Sierra and Bert Bates. Parallel I watched a video course from Simon Roberts (livelessons OCA 8 Programmer I) and took the mock exams from Whizlabs.
These exams were much harder than the real Exam
Often those questions had a real bad intendation, but this sharpened my view. Also support questions were answered quickly.
Hopefully you hear from me soon, publishing my OCP results :-)