StarTrek class hangs

Hi,

When run the following class with midp 2.0, the midlet hangs. I think it
happens in the flushGraphics() method. Does anybody know the solution?

Best regards,

Matheas Manssen

import javax.microedition.midlet.*;
import javax.microedition.lcdui.*;
import javax.microedition.lcdui.game.*;
import java.util.*;
import java.lang.*;

//Bestand: MyGameCanvas.java

class MyTimerTask extends TimerTask {
 private MyGameCanvas canvas;

 public void MyTimerTask( ) {
 }

 public void setCanvas ( MyGameCanvas myGameCanvas ) {
  canvas = myGameCanvas;
 }

 public void run() {
  canvas.update();
 }
}

class MyGameCanvas extends GameCanvas {

 private static int FOCUSAFSTAND = 50;
 private static int STARS = 100;

 private Graphics graphics;
 private Random random;
 int width, height;
 int x, y;
 int range;
 int color;
 int starField[][] = new int [STARS][3];

 public MyGameCanvas( boolean surpressKeyEvents ) {
  super( surpressKeyEvents );

  graphics = getGraphics();
  random = new Random();
  width = getWidth();
  height = getHeight();
  range = Math.max( width, height );

  // vul starField
  for ( int star=0; star< STARS; star++ ) {
   int x, y, z;

   x = random.nextInt() % ( range/2 );
   y = random.nextInt() % ( range/2 );
   z = Math.abs(random.nextInt()) % ( range );

   starField[star][0] = x;
   starField[star][1] = y;
   starField[star][2] = z;
  }

  }

 public void update() {
  color = 0x00000000;
  graphics.setColor( color );
  graphics.fillRect( 0, 0, width, height );

  color = 0x00FFFFFF;
  graphics.setColor( color );
  // Druk starField af
  for ( int star=0; star< STARS; star++ ) {
   int x, y, z;
   int px, py;

   x = starField[star][0];
   y = starField[star][1];
   z = starField[star][2];

   px = ( FOCUSAFSTAND * x ) / (FOCUSAFSTAND + z );
   py = ( FOCUSAFSTAND * y ) / (FOCUSAFSTAND + z );
   // Omrekenen naar coordiantenstelsel van scherm
   px = px + width/2;
   py = py + height/2;
   // Zet ster op scherm
   color = 0x00FFFFFF;
   graphics.setColor( color );

   graphics.drawLine( px, py, px, py );
   // Laat ster een stapje dichterbij komen
   starField[star][2] = ( z-1 );
   if ( starField[star][2] == 0 ) {
    starField[star][2] = range;

   }

  }

  flushGraphics();
 }

}

public class StarTrek extends MIDlet implements CommandListener {

    private Command exitCommand;
    private TextBox textBox;
    private Display display;
    private MyGameCanvas gameCanvas;
    private MyTimerTask timerTask;
    private Timer timer;
    private boolean firstTime = true;

    public void startApp() {
 if ( firstTime ) {
  firstTime = false;
         // Create the abstract command
  gameCanvas = new MyGameCanvas( true );
         exitCommand = new Command("Exit", Command.EXIT, 1);

         gameCanvas.addCommand(exitCommand);
         gameCanvas.setCommandListener(this);

         // Set the MIDlet's display to its initial screen
         display = Display.getDisplay(this);
         display.setCurrent(gameCanvas);

  timerTask = new MyTimerTask();
  timerTask.setCanvas( gameCanvas );
  timer = new Timer();
  timer.schedule( timerTask, 1000, 30);
 }
    }

    public void pauseApp() {
    }

    public void destroyApp(boolean unconditional) {
    }

    public void commandAction(Command command, Displayable screen) {
        if (command == exitCommand) {
         destroyApp(false);
         notifyDestroyed();
        }
    }
}