播放AudioInputStream时出错

此SSCCE在这里是“无效结果”，因为音频无例外地重新启动（尝试至少3次）。

import java.net.URL;import java.awt.event.*;import javax.swing.*;import javax.sound.sampled.*;public class RestartableLoopSound {    public static void main(String[] args) throws Exception {        URL url = new URL( "http://pspre.org/media/leftright.wav");        final Clip clip = AudioSystem.getClip();        AudioInputStream ais = AudioSystem. getAudioInputStream( url );        clip.open(ais);        SwingUtilities.invokeLater(new Runnable() { public void run() {     final JToggleButton b = new JToggleButton("Loop");     ActionListener listener = new ActionListener() {         public void actionPerformed(ActionEvent ae) {  if (b.isSelected()) {      // loop continuously      clip.loop(Clip.LOOP_CONTINUOUSLY);  } else {      clip.stop();  }         }     };     b.addActionListener(listener);     JOptionPane.showMessageDialog(null, b); }        });    }}