I used to be a passive member of JavaRanch and this is the first time I'm active to share my views. I am grateful to Bert Bates and Kathy Sierra for providing such a wonderful book and a great platform for all those who dream about excelling in Java.
Initially, I started to read the K&B book and got confidence after solving the exercises in couple of initial chapters. Then I slowly went through all the chapters. But when I was giving the mock tests, I used to get hardly 70% marks. I picked the questions which went wrong and gone through those specific topics. After a couple of mock tests, I got the scores around 85% but never more than 90%. The real exam questions are not difficult concept wise, but little bit tricky. My observation is that mock exams concentrate more on concepts, but real exam was more of tricky questions like incorrect syntax, accessing variables out of their scopes, missing access specifiers etc.,
15-20% of questions can be solved by eliminating the wrong options among all the available options.
If one knows the exact definitions of encapsulation, coupling & cohesion almost all the OOPS questions can be solved.
My advise to everyone who is preparing for SCJP is to concentrate on those specific topics which went wrong during mock tests rather than reading the entire book number of times.