I'm a true believer and advocate of not using an IDE while studying for
OCAJP (and OCPJP), certainly if you are new to Java or still a junior (and maybe even medior) programmer. Although I have to admit, I did use an IDE myself when I studied for
SCJP 6 and OCAJP 7
The main reason: using a text editor and javac/java is a true simulation of your exam environment, you don't have an IDE on the exam to help you to notify you about compiler errors or classpath issues. You are completely on your own! Using a text editor will improve your code evaluation time and make compiler error spotting much quicker. Another advantage: you'll learn the method signatures of classes in the Java API much faster as well, because you don't have code completion to help you. So you'll memorize much better.
Here you can read the experience of a fellow rancher following this advice.
Back in the days when I studied Java at college, I had to use Notepad, javac and java for the simple reason my old computer wasn't able to run any of the available IDEs
In the beginning I struggled and I made not much progress. But once I had mastered, my Java knowledge improved faster than my classmates. I was even able to assist them to pinpoint the cause of compiler errors they encountered using an IDE. My knowledge of the Java API was also significantly better. And the reason is fairly simple: when you make a mistake using a text editor, you are punished harder than someone using an IDE. You need to adjust your code, compile it again and run it. With an IDE it's all done for you and you don't have to switch between different windows. It's almost some form of conditioning
So you learn very quickly you need
anArray.length and
aString.length() to get the length of respectively an array and a
String.
I used a text editor, javac and java for 1 year, that's why (besides being a java developer for 10 years now) I now can use an IDE for certification preparation myself and advice others not to use an IDE without feeling guilty