I took OCA certification exam on March 2019. It took me around six months to prepared it. And here are all chapters notes and some careful questions from the mock exam I marked.
The material in OCA isn't that hard, but they gonna ask you bunch of trcik questions such as space missing or clousre placement etc...
My suggestion would be go through the study guide book first, get familiar with the basic knowledge, then try to do 1 or 2 mock exams, and go over what you miss on the mock exam, and then go back to the book to restrength the knowledge. Don't do the mock exam multiple times because you would remember the question. Only the first time could be considered the real mock exam, the rest time you retake the mock exam would just be a review.
Some Resources that I use: OCA: Oracle Certified Associate Java SE 8 Programmer I Study Guide: Exam 1Z0-808 4 mock exams on Udemy 4 mock exams on iTestJava
GOOD LUCK HAVE FUN!
