JApplet程序，使用URL类定位资源，不知道为什么总是有异常

package ex18;import javax.swing.*;import java.net.URL;import java.applet.*;public class DisplayImagePlayAudio extends JApplet{    private AudioClip audioClip;        public DisplayImagePlayAudio(){        URL urlForImage = getClass().getResource("E:/学习资料/book/image/denmark.gif");        add(new JLabel(new ImageIcon(urlForImage)));                URL urlForAudio = getClass().getResource("E:/学习资料/book/audio/denmark.mid");        audioClip = Applet.newAudioClip(urlForAudio);        audioClip.loop();    }        public void start(){        if(audioClip != null)  audioClip.loop();    }        public void stop(){        if(audioClip != null)  audioClip.stop();    }}