// 碰撞的小球import javax.microedition.midlet.*;import javax.microedition.lcdui.*;public class BumpingBalls extends MIDlet implements CommandListener {    Display display;  // 設備的顯示器    BallCanvas canvas;  // 用于顯示小球的屏幕     private Command exitCommand = new Command("Exit", Command.EXIT, 1);  //退出命令    public BumpingBalls() {		display = Display.getDisplay(this);	 //取得設備的顯示器		canvas = new BallCanvas(display);  // 實例化canvas對象		canvas.addCommand(exitCommand); // 為canvas加上退出命令		canvas.setCommandListener(this); // 為canvas設置命令監聽者    }	// 重載抽象類MIDlet的抽象方法startApp()    public void startApp() throws MIDletStateChangeException {		canvas.start();    }    	// 重載抽象類MIDlet的方法destroyApp()    public void destroyApp(boolean unconditional) throws MIDletStateChangeException {		canvas.destroy();    }    	// 重載抽象類MIDlet的方法pauseApp()    public void pauseApp(){}	// 實現接口CommandListener的方法    public void commandAction(Command c, Displayable s) {			if (c == exitCommand) {		    try {				destroyApp(false);  // 銷毀程序				notifyDestroyed();  // 通知銷毀程序		    } catch (MIDletStateChangeException ex) {		    }		}    }}