J2ME Hello World NullPointerException

Question

我是J2ME的新手，我复制了一个简单的“Hello world”但是当我运行应用程序时，我得到“nullPointerException”。我在下面添加了代码和错误日志。

这是代码

import javax.microedition.midlet.*;
import javax.microedition.lcdui.*;
public class HelloWorld01 extends MIDlet {
    private boolean paused;
    private Display myDisplay;
    private Hello myScreen;

    public HelloWorld01() {
        paused = false;
    }

    public void startApp() {
        try {
            myDisplay = Display.getDisplay(this);
            myScreen = new Hello();
            myDisplay.setCurrent(myScreen.pPrincipal);
        } catch (Exception e) {
            e.printStackTrace();
        }

    }

    public void pauseApp() {
        paused = true;
        notifyPaused();
    }

    public void destroyApp(boolean unconditional) {
        notifyDestroyed();
    }

    class Hello {

        public Screen pPrincipal = new TextBox("Example", " Hello World", 50,
                TextField.ANY);
    }

}

这是Log

    Installing suite from: file:///C:/Users/emrek/AppData/Local/Temp/_mtj.tmpemrek/Test8068677790959588786.launch/Test.jad
Uncaught exception: java.lang.NullPointerException:   0
 - com.sun.ams.TaskManagerHelperImpl.getTaskInfo(), bci=46
 - com.sun.ams.TaskManagerHelperImpl.startTaskWithOptions(), bci=29
 - com.sun.ams.TaskManagerExtImpl.startTask(), bci=6
 - com.sun.midp.odd.ODTEngineBase.runMIDletSuite(), bci=12
 - com.sun.midp.odd.InstallerListenerWithExecute$1.run(), bci=23
 - java.lang.Thread.run(), bci=5

感谢您的帮助，