SCJP stands for Sun Certified Java Programmer. SCJP is an accreditation attained by a Java programmer who has reached an advanced level of knowledge and skills for certification. It is easy to say how well informed about Java programming, but to convince an employer how good you really are is another type of scenario that sometimes can be a challenge. Showing your credentials and certifications would convince an employer quickly, easily and with no second thoughts due to the quality of the Sun Certifications.
Face it, employers these days prefer to hire an employee who is certified rather than one who is not. But pursuing exams headlong to get certification would be too risky (even if you are confident about your knowledge.) It is always better to be prepared first and anticipate all possible bad outcomes, so that you do not become surprised.
By focusing on the core of APIs of J2SE platform and language syntax, you are dead on target to pass the SCJP examination.
There are tutorials available for those who are interested in taking the exams for SCJP Certification through the Internet. Though SCJP has evolved in the previous versions, SCJP 5.0 is now the current version that is used. Most online help still use sample exams that cover the old versions of SCJP. But these are still reliable since some parts of the current exam still include parts of the previous versions.
These mock exams are important for people who really need help for the real SCJP examination itself. As with all endeavors, being prepared before taking the actual exam will prove to be more helpful than being overconfident to the point of failure.