Java Reference
In-Depth Information
Display 19.3
The
Runnable
Interface
(part 2 of 2)
39
public void
actionPerformed(ActionEvent e)
40 {
41 startThread();
42 }
43
public void
run()
44 {
45 Graphics g = box.getGraphics();
46
for
(
int
y = 0; y < FILL_HEIGHT; y = y + CIRCLE_SIZE)
47
for
(
int
x = 0; x < FILL_WIDTH; x = x + CIRCLE_SIZE)
48 {
49 g.fillOval(x, y, CIRCLE_SIZE, CIRCLE_SIZE);
50 doNothing(PAUSE);
51 }
52 }
53
public void
startThread()
54 {
55 Thread theThread =
new
Thread(
this
);
56 theThread.start();
57 }
58
public void
doNothing(
int
milliseconds)
59 {
60
try
61 {
62 Thread.sleep(milliseconds);
63 }
64
catch
(InterruptedException e)
65 {
66 System.out.println("Unexpected interrupt");
67 System.exit(0);
68 }
69 }
70 }
Self-Test Exercises
1. Because
sleep
is a static method, how can it possibly know what thread it needs
to pause?
2. Where was polymorphism used in the program in Display 19.2 ? (
Hint
: We are
looking for an answer involving the class
Packer
.)
