Hello Guys, I have cleared my IZ0-851 exam OCJP with 100% score. feeling really happy, after 3 years of work I got the
fruit 
I am a software engineer and working on
Java since 3 years but when I started studying for OCJP i.e. 3 months back I was actually struggling for solving answers, as a basic habit you see a code and immediately try to run in eclipse because no 1 is bothered to see the code and actually find the mistakes, I dropped eclipse started practicing on command line which helped me to sharpen my knowledge on Java and yes 100% is possible you just need to focus into right direction
How did I study
1)my work experience helped me a lot I was pretty confident on many things and knew what has to be done and what not
2)
SCJP book by Katherine and Bert (The book is your bible)
3)Java Complete Refernce by Schildt (I don't know how many times I have read this book from 1st page to last page, reading this book since my college days)
4) 1 of my colleague had given the exam 1 month back so took his guidance/advice which helped a lot
5)Solved few online mock tests which I felt were quiet difficult compare to OCJP exam
Reason behind giving OCJP : I am planning to do M.S. from a ivy league university so making my profile strong.
P.S. When you score highest people gonna think you did it via dumps but that should not matter to you
God bless and best luck to everybody who are preparing for OCJP exams aim high aim big