code: public int getObjectCount(int groupID) {
  		if (groupID >= 0 && groupID < objectGroups.size()) {
  			ObjectGroup grp = (ObjectGroup) objectGroups.get(groupID);
  			return grp.objects.size();
  		}
  		return -1;
  	}
docs: Returns the number of objects of a specific object-group.
  
  @param groupID
  The index of this object-group
  @return Number of the objects in the object-group or -1, when error
  occurred.