JAVA播放音乐文件时出现的问题该怎么解决呢

这是我写的代码 private void playBGM(){ try { Clip bgm = AudioSystem.getClip(); InputStream is = this.getClass().getClassLoader().getResourceAsStream("sound/bgm.wav"); AudioInputStream ais = AudioSystem.getAudioInputStream(is); bgm.open(ais); bgm.start(); } catch (LineUnavailableException e) { // TODO Auto-generated catch block e.printStackTrace(); } catch (UnsupportedAudioFileException e) { // TODO Auto-generated catch block e.printStackTrace(); } catch (IOException e) { // TODO Auto-generated catch block e.printStackTrace(); } } 这是抛出的异常,求大佬帮我看看 Exception in thread "main" java.lang.NullPointerException at com.sun.media.sound.SoftMidiAudioFileReader.getAudioInputStream(Unknown Source) at javax.sound.sampled.AudioSystem.getAudioInputStream(Unknown Source)

文件格式用war