J2ME no PalmOS - IndexOutOfBoundsException

import javax.microedition.lcdui.*;
import javax.microedition.midlet.*;

public class GuiTests extends MIDlet 
implements CommandListener {
    // display manager
    Display display = null;
    
    // a menu with items
    List menu = null; // main menu

    // list of choices
    List choose = null;

    // textbox
    TextBox input = null;

    // ticker
    Ticker ticker = new Ticker("Test GUI Components");

    // alerts
    final Alert soundAlert = 
    new Alert("sound Alert");

    // date
    DateField date = new DateField("Today's date: ", DateField.DATE);

    // form
    Form form = new Form("Form for Stuff");
     
    // gauge
    Gauge gauge = new Gauge("Progress Bar", false, 20, 9);

    // text field
    TextField textfield = new TextField("TextField Label", "abc", 50, 0);

    // command
    static final Command backCommand = new Command("Back", Command.BACK, 0);
    static final Command mainMenuCommand = new Command("Main", Command.SCREEN, 1);
    static final Command exitCommand = new Command("Exit", Command.STOP, 2);
    String currentMenu = null;

    // constructor.
    public GuiTests() {
    }

    /**
     * Start the MIDlet by creating a list of
     items and associating the
     * exit command with it.
     */
    public void startApp() throws 
    MIDletStateChangeException {
      display = Display.getDisplay(this);
      // open a db stock file

      menu = new List(
      "Test Components", Choice.IMPLICIT);
      menu.append("Test TextBox", null);
      menu.append("Test List", null);
      menu.append("Test Alert", null);
      menu.append("Test Date", null);
      menu.append("Test Form", null);
      menu.addCommand(exitCommand);
      menu.setCommandListener(this);
      menu.setTicker(ticker);

      mainMenu();
    }

    public void pauseApp() {
      display = null;
      choose = null;
      menu = null;
      ticker = null;
      form = null;
      input = null;
      gauge = null;
      textfield = null;      
    }

    public void destroyApp(boolean unconditional) {
      notifyDestroyed();
    }

    // main menu
    void mainMenu() {
      display.setCurrent(menu);
      currentMenu = "Main";
    }

    /**
     * Test the TextBox component.
     */
    public void testTextBox() {
      input = new TextBox
      ("Enter Some Text:", "", 10, TextField.ANY);
      input.setTicker(new Ticker(
      "Testing TextBox"));
      input.addCommand(backCommand);
      input.setCommandListener(this);
      input.setString("");
      display.setCurrent(input);
      currentMenu = "input";
    }
   
    /**
     * Test the List component.
     */
    public void testList() {
        choose = new List("Choose Items",
        Choice.MULTIPLE);
        choose.setTicker(new Ticker(
        "Testing List"));
        choose.addCommand(backCommand);
        choose.setCommandListener(this);
        choose.append("Item 1", null);
        choose.append("Item 2", null);
        choose.append("Item 3", null);
        display.setCurrent(choose);
        currentMenu = "list"; 
   }

   /**
    * Test the Alert component.
    */
   public void testAlert() {
      soundAlert.setType(AlertType.ERROR);
      //soundAlert.setTimeout(20);
      soundAlert.setString("** ERROR **");
      display.setCurrent(soundAlert);
   }

   /**
    * Test the DateField component.
    */
   public void testDate() {
      java.util.Date now = new java.util.Date();
      date.setDate(now);
      Form f = new Form("Today's date");
      f.append(date);
      f.addCommand(backCommand);
      f.setCommandListener(this);
      display.setCurrent(f);
      currentMenu = "date";
   }

   /**
    * Test the Form component.
    */
   public void testForm() {
      form.append(gauge);
      form.append(textfield);
      for (int i = 0; i < 150; i++) {
         form.append(new StringItem(null, i+"\n"));	
      }
      form.addCommand(backCommand);
      form.setCommandListener(this);
      display.setCurrent(form);
      currentMenu = "form";
   }

   /**
    * Handle events.
    */  
   public void commandAction(Command c,
   Displayable d) {
      String label = c.getLabel();
      if (label.equals("Exit")) {
         destroyApp(true);
      } else if (label.equals("Back")) {
          if(currentMenu.equals("list") 
          || currentMenu.equals("input") ||
               currentMenu.equals("date")
               || currentMenu.equals("form")) {
            // go back to menu
            mainMenu();
          } 

      } else {
         List down = (List)display.getCurrent();
         switch(down.getSelectedIndex()) {
           case 0: testTextBox();break;
           case 1: testList();break;
           case 2: testAlert();break;
           case 3: testDate();break;
           case 4: testForm();break;
         }
            
      }
  }
}