FULL PRODUCT VERSION :
java version "1.6.0_26"
Java(TM) SE Runtime Environment (build 1.6.0_26-b03)
Java HotSpot(TM) Server VM (build 20.1-b02, mixed mode)

ADDITIONAL OS VERSION INFORMATION :
Linux  2.6.35.13-92.fc14.i686.PAE #1 SMP i686 i686 i386 GNU/Linux

EXTRA RELEVANT SYSTEM CONFIGURATION :
cups-1.4.6-1.fc14.i686

A DESCRIPTION OF THE PROBLEM :
Regardless the default media setup in cups, java always uses the first media from ppd.

I sniffered the IPP communication between cups and java:
...Dmedia-defaultiso_a3_297x420mmDmedia-supportediso_a4_210x297mmDiso_a3_297x420mmD...
--> The default media is passed to java

When debugging the IPPPrintService, the  the defaultMediaIndex is 0 and the getAttMap contains only "media-default=media-default" (no valid media) which seems to be the problem.

STEPS TO FOLLOW TO REPRODUCE THE PROBLEM :
1. Add cups printer (as default printer))
2. Change default media size in cups to A3
3. Run code-snippet (see below)

EXPECTED VERSUS ACTUAL BEHAVIOR :
EXPECTED -
The default media size should be A3.
ACTUAL -
The default media is the first media.

REPRODUCIBILITY :
This bug can be reproduced always.

---------- BEGIN SOURCE ----------
import javax.print.PrintService;
import javax.print.PrintServiceLookup;
import javax.print.attribute.standard.Media;


public class TestPrinterDefaultMedia {

    public static void main(final String[] args) {
        final PrintService printService = PrintServiceLookup
                .lookupDefaultPrintService();

        // should return iso-a3
        System.out.println(printService.getDefaultAttributeValue(Media.class));
    }
}
---------- END SOURCE ----------

CUSTOMER SUBMITTED WORKAROUND :
Set default media at top position of media list in ppd file.