Can any one tell me if somebody learned Java and got the Oracle certificate. How much can he earn monthly.

Answer 1

It's hard to find a good answer to your question.
That totally depends on the region you're living in and how much demand there is for Java devs.

Answer 2

It depends on the value of Java developer in your locality and your Lev of experience plus your portfolio.

The tags to your question should've been "Java, developer, Certified, Oracle", because OCA is mainly used when you are dealing with the database administrator that's Oracle Certified Associate