这个关于JSlider的异常是什么意思？

Question

slider = new JSlider(1000, 10000);
            slider.setValue(1000);
            slider.setBounds(new Rectangle(137, 121, 206, 22));
            slider.addChangeListener(new javax.swing.event.ChangeListener()
            {
                  public void stateChanged(javax.swing.event.ChangeEvent changeEvent)
                  {
                        Timer timer = timerThread.getTimer();
                        if(timer != null)
                              timer.setDelay(slider.getValue());
                  }
            });
            jPanel.add(slider, null);class TimerThread
        implements Runnable
{
      Timer timer;      public TimerThread()
      {
      }      public Timer getTimer()
      {
            return timer;
      }      public void run()
      {
            ActionListener actionListener = new ActionListener()
            {
                  public void actionPerformed(java.awt.event.ActionEvent e)
                  {
                        Date dateNow = new Date();
                        java.text.SimpleDateFormat fmt = null;
                        fmt = new java.text.SimpleDateFormat("[yyyy-MM-dd HH:mm:ss.SSS Z]");
                        String strFormat = fmt.format(dateNow);
                        System.out.println(strFormat);
                  }
            };
            timer = new Timer(1000,actionListener);
            timer.start();
            };
      }      public void stop()
      {
            timer.stop();
      }}

Answer 1

明明是个NullPointerException，看看你的timer是不是没有启动