//TODO: is it a good practice to implement all the listener interface in the main frame?
public class FormProgram extends JFrame{
//constructor is used to initialize all screen elements, then show the screen;
public FormProgram(){
IntField jf = new IntField(32);
jf.setSize(30, 100);
this.add("South", jf);
setDefaultCloseOperation(EXIT_ON_CLOSE);
setSize(300, 400);