I am new here so let me introduce myself briefly, my name is Mario Hosmar Giacobbe Ríos and i am from Uruguay (yes!, the marihuana country in southamerica, btw i'm not proud of that ) and a passionate java developer since 2009.
I have just passed the OCA exam last January 15 with 95% and that was a big achievment to my career since i was planning this since 2012 but unfortunately in my country that was not even possible since there were no Pearson Vue centers at all untill last year.
Anyways (no more bla bla ) here is how i prepared the exam:
Books: Oracle Certified Associate Java SE 8 Programmer I Study Guide: Exam 1Z0-808 by Jeanne Boyarsky, Scott Selikoff
Java 8 in Action: Lambdas, Streams, and Functional-style Programming by Mario Fusco and Alan Mycroft
Mock Exams: enthuware.com
The ones in the first book mentioned by Jeanne Boyarsky and Scott Selikoff
And thats all, practise, study, practise and study for 4 months everyday. I followed as a gold rule just to learn something everyday (no matter the big or small the topic is) in about half an hour or hour a day, so i keep on focus and practise as much as possible without stressing myself and that worked like a charm for me.
Good luck for everyone taking this exam, it really worth it!, and i hope my advice works for everyone who reads this topic.