1) Opportunity to learn Java better
Java certifications give you an opportunity to learn Java programming language very closely in a short span of time. You not only learn about basics but also subtle details of essential Java APIs. Syllabus of Java SE 7 exams are designed so well that you will be exposed to key Java concept, object-oriented design patterns, file input-output handling, exception handling, Java database connectivity, Java Generics and collection, Garbage collectors, and different GC algorithms, multi-threading and concurrency and many more key topics are part of certification objective. Once a beginner goes through this rigorous syllabus he is bound to get a very good understand of Java programming language.
2) Help to pass Java written tests
Java Certifications helps the beginner to clear written tests. At fresher level, competition is much higher than at experienced level and many programmers apply for the same job and companies often use written test to filter those large number of candidates. Once you are Java certified, there is very good chance that you will clear all these Java programming written tests with very little or no effort. Some companies even provide direct interview opportunities to Oracle certified Java developers. By the way, ready to prepare with coding questions, because Sun certification hardly tests your programming or coding skill, which is also very important during Java interviews.
3) Hiring Preference
Many government organizations and consultancy companies who works in government project values Java certification highly. Not every Job says that Java certification is a must, but there are certainly few jobs out there, who prefer a certified Java developer than the non-certified one. By passing Java certification like OCA or OCPJP7 with good marks, a beginner improves his chances of getting called from these companies.
4) Confidence Boost
Java certifications give your confidence a huge boost. Even without significant real life Java programming experience, you will feel that you know Java much better, this reflects in your interview and there it matter most. I have seen certified Java programmer performs lot better on core Java questions than normal programmers.
5) Add value to Resume
Java Certification looks very good on the resume. Especially if you don't have outstanding academic records or something on extra curricular which stands out, go for Java certification. This will fill your gaps in the resume. It also sometimes acts as filtering criterion. A hiring manager with 100 of resumes from freshers and junior Java developer has only limited time to conduct interviews. He will certainly call first 10 of them who has either outstanding academic records or Java certifications on their resume.
6) Better Salary
Though it's not guaranteed, I have found that Java certified professional often gets better salary and package then Java developers with same skill set but not certified. One reason of this could be that employer value a Java Certified professional more than those who are not. Which is true, some companies especially mention that they will hire only Oracle Certified Professional. One reason of that is they save time and cost on examining candidate's basic Java skill by various online Java testing sites like Brainbench, which is used by hiring managers to test Java fundamentals.
7) Opportunity to upgrade your Java knowledge
Java is changing and it's changing fast. If you are reading blogs or following release notes of various JDK version, you should know that several new features are added and existing features are improved. Which means, the best practice you follow now may not be relevant when you move to higher Java version.
8) Reimbursement from Employer
Many good companies, start-ups encourage their employee to develop their technical and soft skills. It's a win-win for both company and candidate if he improves himself, that's why many companies pay for your certification cost, which sometimes include the cost of OCPJP and cost of buying some courses or books.
9) Rejuvenate your learning Skill
Just like an artist never satisfied with his art, a programmer should never satisfy with his skill. It's a field of constant learning but like anything else, your learning will get slower with time due to lack of goals, opportunity and doing same time of job again and again. Java Certification provides an opportunity to rejuvenate your learning skill. Every day you learn something new about Java programming language.
10) Recognition in Team
One more reason, why you should get Java certified is to improve your position in the team. I have experience that, passing SCJP in past and OCPJP nowadays with good score improves your impression in the team. People recognize your Java skill more than before and develop a high regard for your Java knowledge. This is really useful, it not only help you to make a good friend, and increase your networking circle. If you participate in Java groups, then becoming Java certified also improves your position among your circle.