這個問題有點無語，目前還不知道這是什麼原因，因為對Eclipse不熟悉

如果用如下程式碼：

URL u = getClass().getResource("src/GUI_Basic/aaaa.wav");
		AudioClip a = Applet.newAudioClip(u);
		a.loop();

Exception in thread "main" java.lang.NullPointerException
	at sun.applet.AppletAudioClip.<init>(AppletAudioClip.java:65)
	at java.applet.Applet.newAudioClip(Applet.java:313)
	at GUI_Basic.Exercise16_20.<init>(Exercise16_20.java:25)
	at GUI_Basic.Exercise16_20.main(Exercise16_20.java:14)
 

File file = new File("src/GUI_Basic/SuperMarry.wav");
		URL url = null;
		try {
			URI uri = file.toURI();
			url = uri.toURL();
		}
		catch (MalformedURLException ex) {
		}
		AudioClip clip = Applet.newAudioClip(url);
		clip.loop();