Menggunakan objek TextBox pada JAVA (J2ME)

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

public class DemoTextBox extends MIDlet
implements CommandListener {
   
  private Display display;
  private TextBox tb;
  private Form formInfo;
  private Alert alert;
  private Command cmdKeluar;
  private Command cmdSetTeks;
  private Command cmdSisipTeks;
  private Command cmdKosongkanTeks;
  private Command cmdInfoTeks;
  private Command cmdKembali;
   
  public DemoTextBox() {
    display = Display.getDisplay(this);
   
    tb = new TextBox("Contoh TextBox", null,
                     256, TextField.ANY);
               
    cmdKeluar  = new Command("Keluar", Command.EXIT, 1);
    cmdSetTeks = new Command("Set Teks", Command.SCREEN, 2);
    cmdSisipTeks = new Command("Sisipkan Teks",
                               Command.SCREEN, 2);
    cmdKosongkanTeks = new Command("Kosongkan Teks",
                                   Command.SCREEN, 2);
    cmdInfoTeks = new Command("Info Teks", Command.SCREEN, 2);

    cmdKembali = new Command("Kembali", Command.SCREEN, 2);

    tb.addCommand(cmdKeluar);
    tb.addCommand(cmdSetTeks);
    tb.addCommand(cmdSisipTeks);
    tb.addCommand(cmdKosongkanTeks);
    tb.addCommand(cmdInfoTeks);
    tb.setCommandListener(this);
  }
   
  public void startApp() {
    display.setCurrent(tb);
  }
   
  public void pauseApp() {
  }
   
  public void destroyApp(boolean unconditional) {
  }
   
  public void commandAction(Command c, Displayable s) {
    if (c == cmdKeluar) {
      destroyApp(true);
      notifyDestroyed();
    } else if (c == cmdSetTeks) {
      tb.setString("Contoh pengesetan teks di dalam TextBox");
    } else if (c == cmdSisipTeks) {
      tb.insert("TEKS SISIPAN", 0);
    } else if (c == cmdKosongkanTeks) {
      if (tb.size() > 0) {
        tb.delete(0, tb.size());
      }
    } else if (c == cmdInfoTeks) {
      formInfo = new Form("Informasi Teks");
      formInfo.append("Teks aktif: " + tb.getString() + "\n");
      formInfo.append("Jumlah karakter: " + tb.size() + "\n");
      formInfo.append("Posisi cursor: " + tb.getCaretPosition());
           
      formInfo.addCommand(cmdKembali);
      formInfo.setCommandListener(this);
      display.setCurrent(formInfo);
    } else if (c == cmdKembali) {
      display.setCurrent(tb);
    }
  }   
}