seeing https://www.dukascopy.com/client/javadoc ... Order.html I can't get back the Id of the account that own that position right?
So I should store somewhere a map account ids => orders ids?

Thanks

No, the interface does not hold such information.
Why should it be? For retrieving account information see:
https://www.dukascopy.com/wiki/#Account_Info
https://www.dukascopy.com/wiki/#Account_Type_and_Login
If you need to find out if a closed order is of particular account, then check it from the order history by using the IHistory.getHistoricalOrderById method.

yes no problem, it's a good thing like you say, the ticket already uniquely identify it
it was more a confirmation question, because I've seen other APIs where they did

ps: https://www.dukascopy.com/wiki/#Account_Info that example is weird to me, why summing amounts if they are on diffrent instruments? it's like summing 4 apples with 3 oranges etc..

You are right, significant part of examples don't have universal applicability - many of them for simplicity assume that there is only one instrument in use.