combobox in j2me

How can I keep the combobox on the form in j2me with out using frameworks?

I have tried this but it is not showing any drop down for selection.

ChoiceGroup CoursePOP = new Choic开发者_StackOverflow中文版eGroup ("Pop Up choice", Choice.EXCLUSIVE, new String[] {"Python", "J2ME","Symbian"}, null);

I have made a combobox by using List which can be done as

List box = new List("Mathematic Operations", List.POPUP);

this.menuList.append("ADD",null);

this.box.append("Subtract",null);

this.box.append("Multiply",null);

this.box.append("Divide",null);

Hope this helped you.

Regards,