Listing 1
1. import javax.microedition.midlet.MIDlet;
2. import javax.microedition.lcdui.*;
3.
4. public class HelloJDJMIDlet extends MIDlet {
5.
6. private Display display;
7. private TextBox text;
8.
9. // provide a command to exit the app
10. private Command bye = new Command("Exit", Command.SCREEN, 12);
11. private CommandListener commandListener = new
CommandListener() {
12. public void commandAction(Command c, Displayable s) {
13. if (c == bye) {
14. destroyApp(true);
15. notifyDestroyed();
16. return;
17. }
18. }
19. };
20.
21. public HelloJDJMIDlet() {
22. display = Display.getDisplay(this);
23. text = new TextBox("Simple MIDlet", "Hello JDJ!", 256, 0);
24. }
25.
26. public void startApp() {
27. text.addCommand(bye);
28. text.setCommandListener(commandListener);
29.
30. display.setCurrent(text);
31. }
32.
33. public void pauseApp() {
34. }
35.
36. public void destroyApp(boolean unconditional) {
37. }
38. }

Listing 2
1. public void paint(Graphics g) {
2. if (!running) {
3. return;
4. }
5.
6. g.setColor(randRange(255), randRange(255), randRange(255));
7.
8. triangle[0] = randRange(w);
9. triangle[1] = randRange(h);
10. triangle[2] = randRange(w);
11. triangle[3] = randRange(h);
12. triangle[4] = randRange(w);
13. triangle[5] = randRange(h);
14.
15. drawPoly(triangle,6,g);
16.
17. }

Listing 3
1. private final int randRange(int n) {
2. int r = random.nextInt() % n;
3. if (r < 0) {
4. r += n;
5. }
6. return r;
7. }
8.
9.
10. private final void drawPoly(int coords[], int numcoords, Graphics g) {
11.
12. ...
13.
14. }

Listing 4
1. public void run() {
2. int n = 0;
3.
4. stopped = false;
5.
6. while (!stopped) {
7. now = System.currentTimeMillis();
8. if (nextTime < now + 15)
9. nextTime = now + 15;
10. try {
11. runner.sleep(nextTime - now);
12. }
13. catch(Exception e){}
14. nextTime = System.currentTimeMillis() + 50;
15.
16. screen.repaint();
17.
18. }
19. }