Did you mean
com.mendix.systemwideinterfaces.connectionbus.data.IDataTable? No, that is not possible. This is an interface and you have to create your own implementation of this interface to be able to instantiate (create) them.
You get instances of a Mendix implementation of IDataTable when you retrieve data via the retrieveOQLDataTable methods in the Core class, but you cannot alter the data of these instances.
If you want fill in Mendix data use the mendix objects. Otherwise you would pass security and other business logic.
If you want to store data in another database look at the database replicator, get the connector logic and fire some insert queries.
It looks like IDatatable is an interop for Excel. Look at the excel java code. I have something in development that can create Excel files by addressing cells e.g. sheet1!a1 = 'first'.
Did you take a look at datasets? They provide an interface for working with tables in mendix. The java version might be useful in your case