JAVA ME 手机程序入门级源码

 一个由 Carol Hamer 写的比较有代表性的源码，作者全力推荐，尤其是对于没有 J2ME 开发经验的朋友。自己动手敲出以下贴出的 Hello.java 和 HelloCanvas.java 源码，并运行，用心体会一下。相信你理解了此源码之后，即可步入 J2ME 开发。
注释都在源码里，运行环境自己配，自己动手看运行效果，理解之后，然后动手修改一下源码，J2ME 开发，你可以的！
Hello.java 源码：
package net.frog_parrot.hello;
import javax.microedition.lcdui.*;
import javax.microedition.midlet.*;
/**
* This is the main class of the hello world demo
*
* @author Carol Hamer
*
*/
public class Hello extends MIDlet implements CommandListener {

/**
* The canvas is the region of the screen that has bean alloted to the game
*/
HelloCanvas myCanvas;

/**
* The Command objects apears as buttons.
*/
private Command exitCommand = new Command("Exit",Command.EXIT,99);

/**
* The Command objects apears as buttons.
*/
private Command newCommand = new Command("Toggle Msg",Command.SCREEN,1);

/**
* initialize the canvas and the commands
*/
public Hello() {
myCanvas = new HelloCanvas(Display.getDisplay(this));
myCanvas.addCommand(exitCommand);
myCanvas.addCommand(newCommand);
myCanvas.setCommandListener(this);
}
//--------------------------------
// implementation of MIDlet

/**
* Start the application
*/
protected void startApp() throws MIDletStateChangeException {
myCanvas.start();
}

/**
* This method is called to notify the MIDlet to enter a paused state.
* The MIDlet should use this opportunity to release shared resources.
*/
protected void pauseApp() {
}

/**
* If the MIDlet was using resources,it should release them in this method
*/
protected void destroyApp(boolean arg0) throws MIDletStateChangeException {
}

//-----------------------
// implementation of CommandListener.
/**
* Respond to a command issued on the Canvas
* (either reset or exit)
*/
public void commandAction(Co