Welcome to CodeRanch Erlanda.
I hope that we find the community here helpful, knowledgeable, sharing and welcoming.
That is unfortunate that you did not succeed with the exam. Please do not feel too discouraged as the exams are difficult.
Some times seasoned developers have troubles with the exam as noted here
https://coderanch.com/t/688492/certification/OCA-Feeling-Inadequate.
Others on this site have also not done that well, here are a few:
https://coderanch.com/t/664886/certification/Failed-exam-advicehttps://coderanch.com/t/669716/certification/Retaking-certification-Exam
You may want to look at some of the stories listed here
https://coderanch.com/wiki/659980/Ocajp-Wall-Fame to see what materials/resources others have used and how they prepared.
A few other notes which may help you out when preparing include:
Do not use an IDE, use a plain/simple editor like Notepad++, Sublime, Vim, etc. IDEs are great for production code, but they tend to hide some of the things that the exam questions you on.Write many programs as you are learning to help with learning. A 20-30 line program can really help you cement a concept like sub classes, visibility and more.You now know some of the areas where your knowledge is lacking so you can hopefully learn those areas better.When taking practice exams look at both the questions/answers you got correct and the one you got incorrect. You may have gotten lucky with a guess or you may have chosen the correct answer for the wrong reason.Many people find that the Enthuware mock exams are a valuable resource to helping preparing for the exam. Last time I checked it was $10 USD, which is not too bad of a price considering all material you get.You may want to try out a different book or two. I used three different books which you can read about here https://coderanch.com/t/685043/certification/passed.If you have any questions about the questions in the study guides post them to this site. There are many people who are very well versed in Java who volunteer their time to help explain not only the questions but the answers.
Most likely you will have to pay for the exam again if you wish to write it once more.