Invalid Jar file

Question

Made a jar file through the wireless toolkit.. and added the jar to my phone via the Nokia PC Suite.. When I try to open the application my phone tells me its on invalid app message and prompts me to delete it.. more often than not i'm making mistakes... any ideas where i'm going wrong here?
Any advice would appreciated....
Thanks in advance

Answer 1

I've tried putting the different sample programs onto my phone. The Game demo works (push puzzle, worm game and tile puzzle). However this ChangeFont demo does not work.
This demo seems simple enough and perhaps from the source code of this demo could someone point out why my phone calls it an invalid application.
Many thanks again..
import javax.microedition.lcdui.*;
import javax.microedition.midlet.*;
import java.io.*;
import java.lang.*;
import javax.microedition.io.*;
import javax.microedition.rms.*;
public class changeFont extends MIDlet { public static final boolean COLOR = false;
public static final boolean DEBUG = false; public static final int WHITE = 0xFFFFFF;
public static final int BLACK = 0x000000;
public static final int BLUE = 0x0000FF;
public static final int LIGHT_GRAY = 0xAAAAAA;
public static final int DARK_GRAY = 0x555555;
private Display myDisplay = null;
private DecodeCanvas decodeCanvas = null;
private boolean painting = false;
private Alert mAlert;
public changeFont() {
     myDisplay = Display.getDisplay(this);
     decodeCanvas = new DecodeCanvas(this);
public void startApp() throws MIDletStateChangeException {
     myDisplay.setCurrent(decodeCanvas);
public void pauseApp() {
protected void destroyApp(boolean unconditional)
throws MIDletStateChangeException {
class DecodeCanvas extends Canvas {
     private changeFont parent = null;
     private int width = getWidth();
     private int height = getHeight();
     public DecodeCanvas(changeFont parent) {
          this.parent = parent;
     public void paint(Graphics g) {
          g.setColor(WHITE);
          g.fillRect(0, 0, width, height);
          Font f1 = Font.getFont(Font.FACE_SYSTEM, Font.STYLE_PLAIN, Font.SIZE_LARGE);
          Font f2 = Font.getFont(Font.FACE_SYSTEM, Font.STYLE_PLAIN, Font.SIZE_MEDIUM);
          Font f3 = Font.getFont(Font.FACE_SYSTEM, Font.STYLE_PLAIN, Font.SIZE_SMALL);
          int yPos = 0;
          if (COLOR)
               g.setColor(BLUE);
          else
               g.setColor(LIGHT_GRAY);
          g.fillRect(0, yPos, width, f1.getHeight());
          if (COLOR)
               g.setColor(WHITE);
          else
               g.setColor(BLACK);
          g.setFont(f1);
          g.drawString("BIG FONT", 0, yPos, Graphics.LEFT | Graphics.TOP);
          yPos = yPos + f1.getHeight() + 10;
          g.setFont(f2);
          //      g.drawLine(0, f1.getHeight() + yPos - 1, width, f1.getHeight() + yPos - 1);
          g.drawString("MEDIUM FONT", 0, yPos, Graphics.LEFT | Graphics.TOP);
          g.setColor(BLACK);
          //g.drawLine(0, f2.getHeight() + yPos - 1, width, f2.getHeight() + yPos - 1);
          yPos = yPos + f1.getHeight() + 10;
          g.setFont(f3);
          g.drawString("SMALL FONT", 0, yPos, Graphics.LEFT | Graphics.TOP);
          yPos = yPos + f1.getHeight() + 10;
          g.drawLine(0, f3.getHeight() + yPos - 1, width, f3.getHeight() + yPos - 1);
          painting = false;
}