How can combine threads and buttons?

I would like to start an application, stop it and restart it again and stop etc. I tried the following code. It does start and stop, but I get an error when I try to restart.

Any suggestions?

  /*  * To change this template, choose
  Tools | Templates  * and open the
  template in the editor.  */

  package testactionevent;

import javax.swing.*; import
  java.awt.<em>; import java.awt.event.</em>;

 /**  *  * @author */ public
  class TestActionEvent extends JFrame
  implements ActionListener{
      private JButton jbtStart = new JButton("Start");
      private JButton jbtStop = new JButton("Stop");
      Thread print100 = new Thread(new SiThread());

public TestActionEvent(){

setTitle("TestActionEvent");

getContentPane().setLayout(new FlowLayout());
getContentPane().add(jbtStart);
getContentPane().add(jbtStop);

jbtStart.addActionListener(this);
jbtStop.addActionListener(this); }
/**
 * @param args the command line arguments
 */
public static void main(String[] args) {

    TestActionEvent frame = new TestActionEvent();
    frame.setTitle("Two buttons");
    frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
    frame.setSize(100, 100);
    frame.setVisible(true);


}

public void actionPerformed(ActionEvent e){

    if (e.getSource() == jbtStart){
       System.out.println("Start ");

       String a = new Boolean(Thread.currentThread().isInterrupted()).toString();
       System.out.println("Start " + a);
       if (!print100.isInterrupted()){
           System.out.println("Startbbbbbbb ");
        print100.start();
       }
    }
    else if (e.getSource() == jbtStop){

        print100.interrupt();
    }
} }
 class SiThread implements Runnable {


public void run() {

    int num = 1;

    System.out.println(" - " + num);

    while (0 == 0){
        num = num +1;
        System.out.println(" " + num);
          if (Thread.interrupted()) {
           System.out.println("Thread is


interrupted ");
          return;
      }

} } }