Java How To Program, Late Objects, 11th Edition

... public void handle(long now) {
28               double elapsedTime = (now - previousTime) / 1000000000.0;
29               previousTime = now;                                      
30               double scale = elapsedTime * velocity;                   
31
32               Bounds bounds = pane.getBoundsInLocal();
33               c.setLayoutX(c.getLayoutX() + dx * scale);
34               c.setLayoutY(c.getLayoutY() + dy * scale);
35
36               if (hitRightOrLeftEdge(bounds)) {
37                  dx *= -1;
38               }
39
40               if (hitTopOrBottom(bounds)) {
41                  dy *= -1;
42               }
43            }
44         }
45
46         timer.start();
47      }
48
49      // determines whether the circle hit left/right of the window
50      private boolean hitRightOrLeftEdge(Bounds bounds) {
51         return (c.getLayoutX() <= (bounds.getMinX() + c.getRadius())) ||
52            (c.getLayoutX() >= (bounds.getMaxX() - c.getRadius()));
53      }
54
55      // determines whether the circle hit top/bottom of the ...