如何停止计时器

Question

我正在使用Netbeans 8.0，我很难停止在GUI中制作的计时器。这是我的代码。

public class Task1 implements Runnable{
    public void run()
    {
        long start = System.currentTimeMillis();
        while (!Thread.interrupted())
        {
            long time = System.currentTimeMillis() - start;
            final long seconds = time / 1000;
            final long min = seconds / 60;
            final long remainingSec = seconds % 60;
            final long hr = min / 60;
            SwingUtilities.invokeLater(new Runnable() {
                 public void run()
                 {
                       jLabel3.setText("Time Passed: " + hr + ":" + min + ":" + remainingSec);
                 }
            });
           try { Thread.sleep(100); } catch(Exception e) {  }
        }
    }

}
Thread t1 = new Thread(new Task1());
    private void jButton1ActionPerformed(java.awt.event.ActionEvent evt) {                                         
    t1.start();
    }                                        

    private void jButton2ActionPerformed(java.awt.event.ActionEvent evt) {                                         
    t1.interrupt(); // this one doesnt stop my timer.
    } 

我制作了两个按钮，jButton1启动计时器，jButton2停止计时器。请指教。