You can find the objectives/topics covered
here.
You can find some free sample questions
here.
You may want to take a few moments and go over some stories from past OCA
test takers which can be found on the OCA Wall Of Fame (
https://coderanch.com/wiki/659980/Ocajp-Wall-Fame).
This could save you time, money and frustration as you can see what resources people have used and how they prepared.