— Scott McNealy, Sun Microsystems Chairman, President and ceo

}
}
each time paintComponent() is 
called, the oval gets painted at a 
different location 
But where do we get the new x and y 
coordinates?
And who calls repaint()?
Sharpen your pencil
See if you can design a simple solution to get the ball to animate from the top left of the 
drawing panel down to the bottom right. Our answer is on the next page, so don’t turn 
this page until you’re done!
Big Huge Hint: make the drawing panel an inner class. 
Another Hint: don’t put any kind of repeat loop in the paintComponent() method.
Write your ideas (or the code) here:
there are no
Dumb Questions

---

384
 
chapter 12
animation using an 
inner class
import javax.swing.*;
import java.awt.*;
public class SimpleAnimation {
int x = 70;
int y = 70;
public static void main (String[] args) {
SimpleAnimation gui = new SimpleAnimation ();
gui.go();
}
public void go() {
JFrame frame = new JFrame();
frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
MyDrawPanel drawPanel = new MyDrawPanel();
frame.getContentPane().add(drawPanel);
frame.setSize(300,300);
frame.setVisible(true);
for (int i = 0; i < 130; i++) {
x++;
y++;
drawPanel.repaint();

try {
Thread.sleep(50);
} catch(Exception ex) { }
}

}
// close go() method
class MyDrawPanel extends JPanel {

public void paintComponent(Graphics g) {
g.setColor(Color.green);