Ok I know this might sound a bit silly, as it depends on the person, but on average how much time should I spend on preparing for SCJP? I already have some experience with Java (a few small and medium projects for my university, from implementing a simple "ships" game to some client-server stuff).
I was thinking about taking it around jun-july '10 so I'd have around 7-8months, is it enough/too much/not enough?
Also I've been looking for a good book, is there anything better than: "Sun Certified Programmer for Java 6 Study Guide" by Kathy Sierra and Bert Bates? And what about some practical questions (like "implement this and this" or "write a piece of code which does...")?
Ah and is it really worth it (I'd spend my own money). I'm not asking if it will make me a better programmer (as I've seen such a thread on stackoverflow alread) but do the employers even care about it?
Answer
It took me 3 weeks to prepare for the Java 6 exam, I have 0 professional Java programming experience. For someone who uses the language daily (like a java programmer) it should be even easier. I was very excited to get it over with as soon as possible, so I ordered the Kathy Sierra SCJP Sun Certified Programmer for Java 6 Study Guide at http://www.amazon.com/SCJP-Certified-Programmer-Java-310-065/dp/0071591060 and one day shipped it to me so that I received it on a Saturday. As soon as it came, I started reading. That took about two weeks as the book is an 800 page monster with some self tests in the book that both give you good practice and teach you some specific details that the book did not mention in the actual chapter (a lot you can guess but not all...). For the last week I reviewed all the 2 Minute Drills and re-read the chapters that were API heavy. Also there are a lot of tables (important string methods, thread methods, file API methods, and concurrency). I also took the two master exams included in the book. I took them in study mode and attempted the question, then if it said wrong, I went and tried to figure out why it is wrong, then I went to the reference/hints if I needed. On the day of the exam I reviewed the File/String/Collections API an hour prior to the exam and took it.
I scored 90% so that's GREAT considering I do not have any Java work experience at all and prepared in 3 weeks. It should be much easier for any professional Java developer to prep/take. Although I have known of Java since it came out, and I used it for the occasional graduate and undergraduate program in college so I'm not totally new. Also, I know other C languages so I am used to much of the control structures, etc... However if I can figure out the API/language workings in three weeks enough to get a 90% any experienced java programmer should have no problem figuring out enough to pass. Still that book is giant, the 2 hours of daily train riding to work was a big help in getting the reading done.
Some people say you have to write a hundred small programs to figure things out. But that book is pretty good on details. The most important thing to write programs about (maybe I wrote 10) are the constructors/initializer blocks/static initializer blocks/to find out exactly what is inherited and to cement the order. And when casting a sub class as its parent, it is important to see what happens when you access the variables/overloaded methods. While the overloaded methods are simple and what is expected, accessing variables is not so straight forward. Trust me, write a few programs about it, especially where the super type/sub type have instance variables with the same name.
I think the main thing I got out of SCJP is a broad overview of the language. Java is a beast, the API/language is huge. Typically I just used the parts of the language I needed for each project/activity in Java and looked up the API as I went. Some key words (like transient) I just did not know. Also some interview trivia (like if you override equals what else must you override) I did not know (at least according to what a friend told me). Also I had no idea about things like the internationalization classes Locale, Calendar, DateFormat, NumberFormat, and Date. Really if I was writing serious Java software, I would probably use Calendar for date arithmetic needs. I don't think it will help me land a Java job as everyone seems to want Java experience prior to even giving you an interview. But if I ever do get an interview, the knowledge I gained from preparing the exam would definitely help me to better answer the questions (though I'm sure a lot of the specific API details will fade with time). Also now I feel more confident with Java. Still I can't say that I can just whip up a Java program on the white board that fully works because the API is very complex. A language like C is pretty small, include stdio.h/stdlib.h/string.h and memorize 30 functions and you can do a lot. Java has way more packages/classes to include and way more API. Also with expressions there are a ton of rules, promotions, casting, autoboxing, etc. which would be really easy to mess up. Though C has precedence hell, with the right parenthesis you can get away with a lot. Java is more strict on things (ie if(0) is an error). But the exam is worth it just for some additional trivia, although the exam is a bit frustrating, and if you look at the book it pretty much tells you that the exam deliberately picks tricky questions and edge cases in an attempt to confuse you. It will deliberately give bad indentation and other stuff to try to be tricky. I hate that because rather than focusing on you knowing the material reasonably, it focuses on trying to confuse you.
One thing of note, don't get thrown by the Master exam. I tried to take one in exam mode, and they gave 75 questions in 1.5 hours and I nearly decided to postpone the exam. The real exam is 60 questions and you get 3 hours. Also the questions on the actual exam are MUCH easier than on the master exam. My master exam score was 37%.... My last two times I just did it in study guide mode, attempted each question/if answer was wrong tired again/viewed reference once with the A exam and once with the B exam... I did fine on the exam and I am really really happy that I did not postpone it over the study guide, because now it is over and I can relax....