The existing class doesn't have a filter on printer device type, although you could add one using getUserFilter as an example.
Once you have the full list of spooled files, you could split them yourself into two groups. Try String prtdevtype = splf.getStringAttribute(ATTR_PRTDEVTYPE);
From this you can tell if you have a text spooled file (*SCS) or one with graphics in it (*IPDS, *AFPDS).