Advance Thanks.i am new to blackberry developement.i try the following code for creating alert using lcdui package.but nothing will coming when i am running

Plz help me.

package alertpack;

import javax.microedition.lcdui.Alert; import javax.microedition.lcdui.AlertType; import javax.microedition.lcdui.Command; import javax.microedition.lcdui.CommandListener; import javax.microedition.lcdui.Display; import javax.microedition.lcdui.Displayable; import javax.microedition.lcdui.Form; import javax.microedition.lcdui.Screen; import javax.microedition.midlet.MIDlet; import javax.microedition.midlet.MIDletStateChangeException;

import net.rim.device.api.ui.Color; import net.rim.device.api.ui.Graphics;

public class alertclass extends MIDlet implements CommandListener {

private Display display;

private Alert alert;

private Form form = new Form("Throw Exception");

private Command exit = new Command("Exit", Command.SCREEN, 1);
//public static void main(String[] args)
//{

//}

private boolean exitFlag = false;

public alertclass(){
    display = Display.getDisplay(this);
    form.addCommand(exit);
    form.setCommandListener(this);
}



protected void destroyApp(boolean unconditional)
        throws MIDletStateChangeException {
    // TODO Auto-generated method stub
    if (unconditional == false) {
        throw new MIDletStateChangeException();
        }

}

protected void pauseApp() {
    // TODO Auto-generated method stub

}

protected void startApp() throws MIDletStateChangeException {
    // TODO Auto-generated method stub
    display.setCurrent(form);

}

public void commandAction(Command c, Displayable d) {
    // TODO Auto-generated method stub

    if (c == exit) {
        try {
        if (exitFlag == false) {
        alert = new Alert("Busy", "Please try again.", null, AlertType.WARNING);
        alert.setTimeout(Alert.FOREVER);
        display.setCurrent(alert, form);
        destroyApp(false);
        } else {
        destroyApp(true);
        notifyDestroyed();
        }
        } catch (Exception exception) {
        exitFlag = true;
        }
        }


}

}