帮忙看看，不知道哪里出了错误

Question

import java.awt.*;
import javax.swing.*;
import java.awt.event.*;
import javax.swing.event.*;
import java.applet.*;public class Player extends JApplet implements ActionListener,ListSelectionListener{
private JButton jb1=new JButton("replay");
private JButton jb2=new JButton("play");
private JButton jb3=new JButton("stop");
private AudioClip sound;
private JList<String>list;
private int temp;
private String currentMusic=new String("haikuo.mid");
private String[] music={"someone like you.mid","make you feel my love.mid",
"don't you remember.mid","haikuo.mid"};
public Player()
{
JFrame frame=new JFrame();
frame.setSize(250,400);
frame.setLocation(new Point(100,300));
frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
JMenuBar bar=new JMenuBar();
JPanel panel1=new JPanel();
JPanel panel2=new JPanel();
frame.setJMenuBar(bar);
    Container con1=frame.getContentPane();
con1.setLayout(new BorderLayout());
panel1.setLayout(new GridLayout(1,3));
panel2.setLayout(new BorderLayout());
JScrollPane jsp;
list=new JList<String>(music);
jsp=new JScrollPane(list,JScrollPane.VERTICAL_SCROLLBAR_ALWAYS,JScrollPane.HORIZONTAL_SCROLLBAR_ALWAYS);
frame.setTitle("music");
bar.add(new JMenu(" "));
panel1.add(jb1);
panel1.add(jb2);
panel1.add(jb3);
panel2.add(panel1,BorderLayout.NORTH);
panel2.add(jsp,BorderLayout.CENTER);
con1.add(panel2,BorderLayout.CENTER);
    jb1.addActionListener(this);
        jb2.addActionListener(this);
        jb3.addActionListener(this);
        list.addListSelectionListener(this);
        frame.setVisible(true);
}
public void valueChanged(ListSelectionEvent e)
{
temp=list.getSelectedIndex();
currentMusic=music[temp];
}
 public void actionPerformed (ActionEvent e)
 {
 sound=getAudioClip(getDocumentBase(),currentMusic);
         if(e.getSource()==jb1)
          sound.play();
          else if(e.getSource()==jb2)
            sound.loop();
           else
           sound.stop();
 }
public static void main(String[] args)
{
new Player();
}
}

Answer 1

把JList后面的<String>去掉就可以了吧

Answer 2

它就显示这样，然后在dos的AppletViewer打开显示启动：未初始化
Exception in thread "AWT-EventQueue-0" java.lang.NullPointerException
at java.applet.Applet.getDocumentBase(Unknown Source)
at Player.actionPerformed(Player.java:57)
at javax.swing.AbstractButton.fireActionPerformed(Unknown Source)
at javax.swing.AbstractButton$Handler.actionPerformed(Unknown Source)
at javax.swing.DefaultButtonModel.fireActionPerformed(Unknown Source)
at javax.swing.DefaultButtonModel.setPressed(Unknown Source)
at javax.swing.plaf.basic.BasicButtonListener.mouseReleased(Unknown Source)
at java.awt.Component.processMouseEvent(Unknown Source)
at javax.swing.JComponent.processMouseEvent(Unknown Source)
at java.awt.Component.processEvent(Unknown Source)
at java.awt.Container.processEvent(Unknown Source)
at java.awt.Component.dispatchEventImpl(Unknown Source)
at java.awt.Container.dispatchEventImpl(Unknown Source)
at java.awt.Component.dispatchEvent(Unknown Source)
at java.awt.LightweightDispatcher.retargetMouseEvent(Unknown Source)
at java.awt.LightweightDispatcher.processMouseEvent(Unknown Source)
at java.awt.LightweightDispatcher.dispatchEvent(Unknown Source)
at java.awt.Container.dispatchEventImpl(Unknown Source)
at java.awt.Window.dispatchEventImpl(Unknown Source)
at java.awt.Component.dispatchEvent(Unknown Source)
at java.awt.EventQueue.dispatchEventImpl(Unknown Source)
at java.awt.EventQueue.access$000(Unknown Source)
at java.awt.EventQueue$3.run(Unknown Source)
at java.awt.EventQueue$3.run(Unknown Source)
at java.security.AccessController.doPrivileged(Native Method)
at java.security.ProtectionDomain$1.doIntersectionPrivilege(Unknown Source)
at java.security.ProtectionDomain$1.doIntersectionPrivilege(Unknown Source)
at java.awt.EventQueue$4.run(Unknown Source)
at java.awt.EventQueue$4.run(Unknown Source)
at java.security.AccessController.doPrivileged(Native Method)
at java.security.ProtectionDomain$1.doIntersectionPrivilege(Unknown Source)
at java.awt.EventQueue.dispatchEvent(Unknown Source)
at java.awt.EventDispatchThread.pumpOneEventForFilters(Unknown Source)
at java.awt.EventDispatchThread.pumpEventsForFilter(Unknown Source)
at java.awt.EventDispatchThread.pumpEventsForHierarchy(Unknown Source)
at java.awt.EventDispatchThread.pumpEvents(Unknown Source)
at java.awt.EventDispatchThread.pumpEvents(Unknown Source)