J2ME: Program Agen Pulsa 0.0.1 (#1)

import javax.microedition.midlet.*;
  import javax.microedition.lcdui.*;
  /**
  * @author Didik Kurniawan
  * Jurusan Ilmu Komputer FMIPA Universitas Lampung
  */
  public class AgenPulsa extends MIDlet implements CommandListener{
  List namaOperator;
  List telkomsel, indosat,xl,three;
  Display display;
  Command ok =new Command("OK",Command.OK,0);
  Command exit =new Command("Exit",Command.EXIT,0);
  Command kembali =new Command("Back",Command.BACK,0);
  Command kirim = new Command("Kirim",Command.OK,0);
  Form form=new Form("No Tujuan");
  TextField noTujuan=new TextField(null,null,32,TextField.PHONENUMBER);
  public AgenPulsa(){
  namaOperator=new List("Operator",List.IMPLICIT);
  namaOperator.append("Telkomsel", null);
  namaOperator.append("Indosat", null);
  namaOperator.append("XL", null);
  namaOperator.append("Three", null);
  namaOperator.addCommand(ok);
  namaOperator.addCommand(exit);
  namaOperator.setCommandListener(this);
  
  telkomsel=new List("Telkomsel",List.IMPLICIT);
  telkomsel.append("5K",null);
  telkomsel.append("10K",null);
  telkomsel.append("20K",null);
  telkomsel.append("25K",null);
  telkomsel.append("50K",null);
  telkomsel.append("100K",null);
  telkomsel.addCommand(ok);
  telkomsel.addCommand(exit);
  telkomsel.addCommand(kembali);
  telkomsel.setCommandListener(this);
  
  indosat=new List("Indosat",List.IMPLICIT);
  indosat.append("2K",null);
  indosat.append("5K",null);
  indosat.append("10K",null);
  indosat.append("25K",null);
  indosat.append("50K",null);
  indosat.append("100K",null);
  indosat.addCommand(ok);
  indosat.addCommand(exit);
  indosat.addCommand(kembali);
  indosat.setCommandListener(this);
  
  xl=new List("XL",List.IMPLICIT);
  xl.append("1K",null);
  xl.append("5K",null);
  xl.append("10K",null);
  xl.append("25K",null);
  xl.append("50K",null);
  xl.append("100K",null);
  xl.addCommand(ok);
  xl.addCommand(exit);
  xl.addCommand(kembali);
  xl.setCommandListener(this);
  
  three=new List("Three",List.IMPLICIT);
  three.append("1K",null);
  three.append("2K",null);
  three.append("3K",null);
  three.append("4K",null);
  three.append("5K",null);
  three.append("10K",null);
  three.append("20K",null);
  three.append("30K",null);
  three.append("50K",null);
  three.append("100K",null);
  three.addCommand(ok);
  three.addCommand(exit);
  three.addCommand(kembali);
  three.setCommandListener(this);
  
  form.append("Isi Pulsa");
  form.append(noTujuan);
  form.addCommand(ok);
  form.addCommand(kembali);
  form.addCommand(kirim);
  form.addCommand(exit);
  form.setCommandListener(this);
  
  }
  public void startApp() {
  if (display==null){
  display=Display.getDisplay(this);
  display.setCurrent(namaOperator);
  }
  }
  
  public void pauseApp() {
  }
  
  public void destroyApp(boolean unconditional) {
  }
  public void commandAction(Command c, Displayable d ){
  if (c==exit) {
  destroyApp(true);
  notifyDestroyed();
  } 
  else if(c==ok && d==namaOperator){
  if (namaOperator.getSelectedIndex()==0) {
  display.setCurrent(telkomsel);
  } 
  else if (namaOperator.getSelectedIndex()==1){
  display.setCurrent(indosat);
  }
  else if (namaOperator.getSelectedIndex()==2){
  display.setCurrent(xl);
  }
  else if (namaOperator.getSelectedIndex()==3){
  display.setCurrent(three);
  }
  } 
  else if(c==kembali && (d==telkomsel || d==indosat || d==xl || d==three)){
  display.setCurrent(namaOperator);
  }
  else if(c==kembali && d==form){
  display.setCurrent(namaOperator);
  }
  else if (c==ok && (d==telkomsel || d==indosat || d==xl || d==three)){
  display.setCurrent(form); 
  }
  
  }
  }