How to join two or more than two SAP tables data

I am a java developer and started using JCO recently.

With the help of other threads , I am able to retrieve data from a single table using "RFC_READ_TABLE"

My requirement is :

1. Get the data from two or more tables

2. Do a outer/inner join on those tables based on some column

Is this possible using JCO.

If not , what is the best way to do that in Java.

Thanks

Vishwam