If you download the 1.3 version of the PetStore demo, there are UML diagrams in folders labeled UML for some of the modules (ex. src\components\catalog\uml).
I don't know if Sun intends this to be a hint for those of us studying for SCEA, but there really aren't many diagrams for the PetStore. I found 2 class diagrams and one use case - though I can't view the use case as it's a .PGML file and I haven't found a viewer for it yet
SCJP, SCJD, SCEA 5 "Any sufficiently analyzed magic is indistinguishable from science!" Agatha Heterodyne (Girl Genius)