import javax.microedition.lcdui.Command;

 import javax.microedition.lcdui.CommandListener;

 import javax.microedition.lcdui.Display;

 import javax.microedition.lcdui.Displayable;

 import javax.microedition.lcdui.TextBox;

 import javax.microedition.midlet.MIDlet;

 import javax.microedition.midlet.MIDletStateChangeException;

 public class main extends MIDlet implements CommandListener {

     private Command exitCom;

     private Display ds;

     private TextBox tb;

     //构造函数

     public main() {

         // TODO Auto-generated constructor stub

         ds=Display.getDisplay(this);//创建Display类一个实体

         exitCom=new Command("Exit",Command.EXIT,1);//创建Command对象一个实体，并设置Exit命令用于退出这个MIDlet

         tb=new TextBox("Hellow MIDlet","Hellow World",15,0);//创建用来输出东西的TextBox对象

         tb.addCommand(exitCom);//使Command对象和TextBox关联起来

         tb.setCommandListener(this);//当TextBox显示在屏幕上时，使CommandListener响应发生的事件

     }

     protected void destroyApp(boolean arg0) throws MIDletStateChangeException {

         // TODO Auto-generated method stub

     }

     //当系统要求MIDlet暂停时调用

     protected void pauseApp() {

         // TODO Auto-generated method stub

     }

     //第一次启动或者暂停后重启时由系统调用startApp()方法

     protected void startApp() throws MIDletStateChangeException {

         // TODO Auto-generated method stub

         ds.setCurrent(tb);//将构造函数中的TextBox设置为当前的屏幕

     }

     //用户触发任何Command是，做出回应，系统会自动调用这个方法

     public void commandAction(Command arg0, Displayable arg1) {

         // TODO Auto-generated method stub

         if(arg0==exitCom){

             try {

                 destroyApp(false);

                 notifyDestroyed();

             } catch (MIDletStateChangeException e) {

                 // TODO Auto-generated catch block

                 e.printStackTrace();

             }

         }

     }

 }