rosjava: how to call Services of move_base

I want to call the costmap_clear service of a rosndk native move_base node from ROSjava. I found an example in the Rosjava docu. But i cant see the service when i start move_base. Its not listed in rosnode info and not in rosservice list. I tried starting the move_base node on my pc but still no services.... Do i have to somehow start the service before i can call it? Thanks in advance