Object overloading (data)

In building an API on the i5 with RPGIV which is intended to be callable
from native and web applications I have come across a possible problem that
I have not encountered before. 
 
The API is used to select from a list of addresses, for a customer location,
from a USPS City/State/Zip table and a USPS Street address table, scored by
how well the address matches the user provided information. Depending on the
user provided information the city state zip lookup may result in more than
1 match, e.g.. If the user only provides the city and state and that city
has more than one zip code the API needs to return the list (data
structure/object) to the caller which will display the list to the user who
will select the appropriate zip code and call the API again with the
additional information (zip code). The API will then find a single match in
the USPS City/State/Zip table and continue on to lookup the street address
from the user provided information, and return a list of matches to the
caller.
 
In RPGIV I am overloading the data structure by using the first 10 bytes of
the structure to "name" the format and using the larger of the two
structures as the procedure return variable definition. The calling code
looks a the first 10 bytes and determines if the API is returning the
City/State/Zip structure or the Address structure and does the appropriate
processing.
 
Now, finally, to my question. If the caller is a Java method can it
determine, using the first 10 bytes, if the object/structure returned to it
is a City/State/Zip or Address object?
 
Is there a better way to handle structure/object return value overloading
for RPGIV/Java?
 
Thanks
Duane Christen



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