Hi Mohan,
The
SCJP FAQ should answer many of your initial questions. In general, I'd recommend that you take the Java 5 (a.k.a. 1.5) exam instead of the 1.4 exam, unless you have a special reason for choosing otherwise. A lot of new language features were added in Java 5, and now that Java 6's already out, the value of a SCJP 1.4 certification is probably on a steep decline.
The required preparation time will depend a lot on your own ability, experience, and comfort level. Have you had much programming experience aside from your six months of Java work? Do you have a degree or other formal training that involved substantial Java coding? If your answer to both is no, I'd say that
you should give yourself at least 3-4 months (with at least 3 hours per day) to prepare for the exam. If you do have substantial experience, you can probably get by with 1-2 months or less (I took my
test after only two weeks of preparation, but I was aided by my two degrees in CS and Software Engineering, plus several years of Java programming experience
).
A good first step would be to try out an SCJP mock exam or (better yet) Sun's own free
SCJP proficiency assessment test. If you can get at least 30% of those questions right, you're in very good shape and can probably get by with less preparation time.
[ October 31, 2007: Message edited by: Kelvin Lim ]