Just in case you still follow this thread
Skumar Patel, I would count a few weeks depending on the experience and time you have.
This should give you enough time to read the book and practice the exercises or other excerpts of code you will find there.
Myself, as a Java programmer with 10 years of experience, I expect to finish one or two chapter(s) of the OCP 17 book every week.
In total, I would say at least 50 hours, spread (in my case) on about eight weeks (two months).
How do I know this is enough? Practice, practice, practice.
When I can answer all questions of the book without a doubt.
When I can answer all the Enthuware questions without a doubt.
Then I know I am ready.
Hope this helps.