I finally did it - today I passed the
Java 11 OCP exam with 87%.
It was a long journey, it all started almost a year ago (9-10 months more precisely). I wanted to take on the old 1Z0-815 and 1Z0-816 exams, like everyone else. I was prepared to take the first one like 6 months ago, but hours before my appointment a techical failure happened at the
test center and they had to cancel it. I was very very lucky, because the same day I learned about the new exam, 1Z0-819. I was happy to find out that the exam lasts just 90 minutes now instead of 180 for the old one. The bad part was that 1Z0-819 includes double the study material in a quarter of the time.
So how was it, you ask? Well, it was a lot to take in. Lots and lots of methods to memorize, corner cases, classes - but hard work pays off I guess.

I am working a full time job so I was familiar with some of the concepts, but I had to learn lots of others. I studied in the afternoon - at first I was't doing it every day but then it became routine.
I want to thank Jeanne Boyarsky and Scott Selikoff. Really, thank you. Your study guides have been excellent. I started with the 1Z0-815 guide then went all in with the complete study guide which came later. The book covers like 95% of the exam and everything is explained clearly and concisely.
I was ready to take the first exam when the new one came out, so I didn't insist on the first part of the complete study guide. I started reading the second part - I was doing a chapter per week (includong the quiz at the end of each chapter). As I was reading alone, I noted down some takeways for each section. Upon finishing the book, I had around 150 pages written by hand (it's easier for me to learn new stuff like that - it helps me memorize).
After finishing the book I went ahead and read my own notes until I was comfortable with all material. I had to read everything 4 times.
In the meantime I got the Enthuware model exams and started doing one a day in the weeks before the exam. If you want to be prepared for the exam, buy the Enthuware mock exams - trust me, it's worth it. They have been life saving.
As I was doing the mock exams I started noting down all the mistakes I've made which also helped me a lot. The days before the exam I went through those. My average score in the Enthuware exams was 81% and I was pretty happy and confident about the real exam.
And now the exam day: well, even of I was pretty confident I was also very nervous. I've chosen taking the exam at a test center near me - I think it really helps you get in the mood, avoiding getting too comfortable at home.
It turned out the mock exams were way closer to the real thing than I initially thought! The difference was that there were a lot of questions with lots of code to go through - I was pretty scared seeing them because they were the most time consuming.
My main advice would be to practice your time management skills. I finished the exam with 4 minutes to go, which is...well, close. Considering the lengthy questions, be careful. I had 15 minutes to go and 10 more questions to solve so I had to rush it in the end, but it turned out well. The questions were not overly complicated besides that - if you read the material thoroughly and do the mock exams you'll be fine.
I had a lot of questions about generics, functional interfaces (& lambdas) and streams. Understand these very well, they're critical. I also had some questions on modules but they were fine.
In the end I'm happy that I took the exam and I'm happy that I can finally take a break.
Phew, this was a long post, but I hope it helps!