Java Programming

i am trying to modify and existing open source program that emulates a virtual tabletop surface for multiple people on via networking. at current, there are two "layers" to the table: one for map backgrounds, and one for 'objects' on the map-people, buildings, vehicles, etc. i constantly run into problems trying to prevent images on one of the layers from overlapping and blocking off each other visually.

i have not been able to find anything in the api yet, perhaps my keywords are not the right ones. what i need is to find out how to assign a "z-order" index to each instance of an image placed on the virtual tabletop. much like dhtml has a "z-layer" property, i would like this program to redraw the visible images in a specific order, determined by thier "z-order" variable value.

i thought this would be the simplest way to emulate multiple layers within the program. the ultimate goal being sought after here is to have multiple "vertical" layers for holding the objects on the map.

thanks for any help with this. =)