This is entirely up to you. Three weeks sounds short but depending on how much you can cram in those 10 hours it might lead you to success. Most participants (including me) spent 2-3 hours a day over a span of 2-3 months. This statistic is based on the threads that I have read over the last few years, so take that with a grain of salt
Purpose of the exam is to understand the basics thoroughly. If you are just giving the exam to get the certification, you might get the
certificate in hand with even good percentage, but as it is more like cramming, it won't do much good. Even very experienced programmers
take like 2 months to give the exam, because it really test your knowledge and concepts about the API. I will suggest if you are not in a hurry,
take your time and understand the basics. You will do much better then and it's gonna be worth while as well.
Many people think SCJP exam can't make you a good programmer, but i will say that if you really give the exam with honesty and proper understanding,
it gives you a very solid foundation to be a good programmer.
hi deepak, vicky, nitesh and prithvi, thanks alot for your repsonse for my post, i will definitely take into consideration each and every word what you people suggested to me, as you people said for certification purpose 3 weeks are enough but for gaining knowledge its not enough time this is really true, i will try to spend few more weeks to gain knowledge and good percentage in SCJP exam, wish me good luck guys have a nice day.