OnlineHelp例子运行时异常：IllegalArgumentException
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? OnlineHelp例子运行时异常：IllegalArgumentException??
? //-----------------------------
? // 这是从书中拷贝下来的。编译时没错，运行时发现此异常。
? // 请问错在哪？
? //-----------------------------
? import javax.microedition.midlet.*;
? import javax.microedition.lcdui.*;
? public class OnlineHelp extends MIDlet implements CommandListener
? {
? private Display display;
? private Command back;
? private Command exit;
? private Command help;
? private Form form;
? private TextBox helpMesg;
? public OnlineHelp()
? {
? display = Display.getDisplay(this);
? back = new Command("Back", Command.BACK, 2);
? exit = new Command("Exit", Command.EXIT, 1);
? help = new Command("Help", Command.HELP, 3);
? form = new Form("Online Help Example");
? helpMesg = new TextBox("Online Help", "Press Back to return to the previous screen or press Exit Exist to close this program.", 81, 0);
? helpMesg.addCommand(back);
? form.addCommand(exit);
? form.addCommand(help);
? form.setCommandListener(this);
? helpMesg.setCommandListener(this);
? }
? public void startApp()
? {
? display.setCurrent(form);
? }
? public void pauseApp()
? {
? }
? public void destroyApp(boolean unconditional)
? {
? }
? public void commandAction(Command command,
? ? Displayable displayable)
? {
? if (command == back)
? {
? display.setCurrent(form);
? }
? else if (command == exit)
? {
? destroyApp(false);
? notifyDestroyed();
? }
? else if (command == help)
? {
? display.setCurrent(helpMesg);
? }
? }
? }
?

------解决方法--------------------
? 刚才看了很久也没有发现问题
? 亲自在JB里运行了一下发现确是有IllegalArgumentException异常抛出
? 根据异常信息步入原来是这一句的问题
? helpMesg = new TextBox("Online Help", "Press Back to return to the previous screen or press Exit Exist to close this program.", 81, 0);