I just returned from Pearson VUE Testing Center, got through 1Z0-809 with 78%. I think it is worth sharing my experience as I did not have past Java experience. I used to google and write some sample programs.
I have past experience in coding C, C++ and Eiffel OOPL.
I decided to do Java certification (I was not sure that we've to pass two levels to get Professional Certification). After looking at Oracle Certification site, I got to know that we have many versions and I decided to go for latest one available which is 1.8 and it has 1Z0-808 and 1Z0-809.
I googled and found that there is a good study guide (OCA: Oracle Certified Associate Java SE 8 Programmer I Study Guide: Exam 1Z0-808 - by Jeanne Boyarsky, Scott Selikoff). I immediately bought it and started reading it. In very first few pages of that book, they recommended to first go through books similar to "Head First Java" if one does not have prior Java experience. So, I stepped back and finished reading Head First Java book first. And, then returned to this book. This was really important part of my foundation as a java programmer. I spent around 2 months to finish reading (along with practicing). Also solved exercises given by Jeanne and Scott in their web site (it comes free if we buy OCA book mentioned above). And, finally I wrote exam on 1st September 2015 and passed with 85%. Hmm, not bad but, there was bigger challenge in my mind that is 1Z0-809. And, I know it is very big challenge for me considering my past experience with java and the study tools we have (we do not have a study guide on 1Z0-809 yet). There is a study guide for 1.7 (Kathy Sierra and Bert Bates).
I started gathering information about my next step and I found https://coderanch.com/t/653042/java-programmer-SCJP/certification/OCPJP-Java-SE-Booked giving some direction on how we could plan preparation. I started preparing for this from 1st week of September and read OCP7 guide mentioned above and "Java SE 8 for the Really Impatient" book. I spent over 2 and half months on preparation (about 150 hours of preparation). I took Jeanne Boyarsky and couple of others who passed this exam without study guide as my inspiration and prepared for it. Practiced lot of examples. There were ups and downs during my preparation. I used to doubt whether I could really pass it or not considering the difficulty of these topics, especially while practicing Threads and Concurrency . However, I used to take some break and come back to preparation and practicing. Apart from above two books I did lot of reading in Online Java Docs and browsed most of the API classes for Streams, Collections, java.util.concurrent.* package, IO and JDBC related packages.
I was a winner of 1Z0-810 MyExamCloud Mock tests. So, I solved all those tests couple of times. Luckily, I did not memorize the questions as my memory is not that good . Also, I used Enthuware 1Z0-809 mock tests. It has a very good composition of tests. There are 7 practice tests (6 regular and 1 unique test for last day). I used first three exams for interactively writing exam and practicing if I encounter a new kind of question. Also, used to refer to Online Docs if I have any questions about some classes or methods. And, then I solved last 3 and 1 unique tests on my own (without practicing). I had a goal of finishing this before December as I had next commitment, so had to finish it before December 2015.
In summary, it took almost 5 months for me to get through both 1Z0-808 and 1Z0-809 with my average reading capabilities. And, below things helped me a lot to achieve this:-
1. Head First Java book
2. OCA guide by Jeanne Boyarsky, Scott Selikoff
3. OCA/OCP guide by Kathy Sierra and Bert Bates
4. Java SE 8 for the Really Impatient
6. Enthuware Practice Tests
7. MyExamCloud Practice Tests
NOTE: Never used any IDE for practicing. Just NOTEPAD was my buddy .
If you are starting/planning to prepare now, I would suggest you to continue reading OCA guide mentioned above and wait for OCP guide that Jeanne is working on.