Well the best way i would suggest would be to study on your own and try to
get in habbit of reading books . When we are in college level we usually
dont try to get these kinds of habbit as they are hard to adopt but after
coming in professional life ppl usually develop this thing on there own .
So the best thing would be to get some books and start reading and writing
some key points on a register or somthing .. the books that i think are
really good are

1. Beginning Java 2 ( Wrox )
2. Thinking in Java ( Intermediate level )

if you read the first book then you should switch to the second one ... you
dont need to read the 2 book completly , i think reading 400-500 pages
cover all the stuff that is for JCP.

secondly i am sending these sample papers so if you give them then they
will also help you a lot . Dont feel down if u dont score good marks in
these papers in 1or 2 or 3 goes ... keep on reading from book and keep on
giving sample papers and after that JCP would be a piece of Cake.