code: public void moveItem(Point oldCoordinates, Point newCoordinates) {
  	assertEDT();
  	if (oldCoordinates == null || newCoordinates == null) {
  	    throw new IllegalArgumentException("Coordinates cannot be null");
  	}
  	if (getPanelAt(newCoordinates).hasModel()) {
  	    throw new IllegalStateException(
  		    "New position contains a model in the UI already. New position = " + newCoordinates);
  	}
  	if (!getPanelAt(oldCoordinates).hasModel()) {
  	    throw new IllegalStateException("Old position doesn't contain a model in the UI. Old position = "
  		    + oldCoordinates);
  	}
  	// all good
  	Drawable item = getPanelAt(oldCoordinates).getModel();
  	removeItem(oldCoordinates);
  	addItem(newCoordinates, item);
  
      }
docs: Changes the position of the item in the specified location
  
  @param oldCoordinates position of the item to move
  @param newCoordinates position to move the item to