Whats the point in getting a OCJP or SCJP certificate ?

Okay, this problem may be specific to me. Many things are covered in OCJP. I can remember most of them after preparing for 3 months and pass the test. Then what ? 2-3 months later, I am doing code at an internship which hardly uses
few of these concepts. But, the code does significant work. Anyway I forgot most of these concepts. But, they are still there in my notes for the OCJP which I finally decided not to take.

I would rather do projects (big or small, personal or for a company) that will use many of these concepts. That way, I can remember and appreciate the need for these concepts without memorizing them to pass an exam and flash
a (worthless) certificate at every interview that i go to.

Which projects or kinds of project could use a lot of concepts at one time ?

I couldn't agree more. There are so many inter related technologies and frameworks, so work on tutorials, self-taught projects, open source contributions, and part-time volunteer work. Many quality developers don't have any certifications. They thrive on ongoing learning, passion for what they do, and hands-on accomplishments. Along the way, I recommend you start a blog and capture your experience.