Note: painting is done in order objects were added,
 * so objects added last are drawn "on top" of others.
 * Use raise/lower methods to change the object z-ordering, if needed.
Note: painting is done in order objects were added,
 * so objects added last are drawn "on top" of others.
 * Use raise/lower methods to change the object z-ordering, if needed. | GraphicCanvasVisualizer.java