Manipulate Swing Timer with JButton/ActionListener

Question

I'm using Swing Timer and trying to make a stop button for the clock. I'm trying to use "timer.stop();" in my ActionListener, but it is throwing errors and not stopping the clock. Looked around and couldn't find a solution. Any suggestions?

These are the errors:

"Exception in thread "AWT-EventQueue-0" java.lang.NullPointerException
at tests.TwoPerson$2.actionPerformed(TwoPerson.java:32)
at javax.swing.AbstractButton.fireActionPerformed(AbstractButton.java:2022)
at javax.swing.AbstractButton$Handler.actionPerformed(AbstractButton.java:2348)
at javax.swing.DefaultButtonModel.fireActionPerformed(DefaultButtonModel.java:402)
at javax.swing.DefaultButtonModel.setPressed(DefaultButtonModel.java:259)
at javax.swing.plaf.basic.BasicButtonListener.mouseReleased(BasicButtonListener.java:252)
at java.awt.Component.processMouseEvent(Component.java:6535)
at javax.swing.JComponent.processMouseEvent(JComponent.java:3324)
at java.awt.Component.processEvent(Component.java:6300)
at java.awt.Container.processEvent(Container.java:2236)
at java.awt.Component.dispatchEventImpl(Component.java:4891)
at java.awt.Container.dispatchEventImpl(Container.java:2294)
at java.awt.Component.dispatchEvent(Component.java:4713)
at java.awt.LightweightDispatcher.retargetMouseEvent(Container.java:4888)
at java.awt.LightweightDispatcher.processMouseEvent(Container.java:4525)
at java.awt.LightweightDispatcher.dispatchEvent(Container.java:4466)
at java.awt.Container.dispatchEventImpl(Container.java:2280)
at java.awt.Window.dispatchEventImpl(Window.java:2750)
at java.awt.Component.dispatchEvent(Component.java:4713)
at java.awt.EventQueue.dispatchEventImpl(EventQueue.java:758)
at java.awt.EventQueue.access$500(EventQueue.java:97)
at java.awt.EventQueue$3.run(EventQueue.java:709)
at java.awt.EventQueue$3.run(EventQueue.java:703)
at java.security.AccessController.doPrivileged(Native Method)
at java.security.ProtectionDomain$JavaSecurityAccessImpl.doIntersectionPrivilege(ProtectionDomain.java:76)
at java.security.ProtectionDomain$JavaSecurityAccessImpl.doIntersectionPrivilege(ProtectionDomain.java:86)
at java.awt.EventQueue$4.run(EventQueue.java:731)
at java.awt.EventQueue$4.run(EventQueue.java:729)
at java.security.AccessController.doPrivileged(Native Method)
at java.security.ProtectionDomain$JavaSecurityAccessImpl.doIntersectionPrivilege(ProtectionDomain.java:76)
at java.awt.EventQueue.dispatchEvent(EventQueue.java:728)
at java.awt.EventDispatchThread.pumpOneEventForFilters(EventDispatchThread.java:201)
at java.awt.EventDispatchThread.pumpEventsForFilter(EventDispatchThread.java:116)
at java.awt.EventDispatchThread.pumpEventsForHierarchy(EventDispatchThread.java:105)
at java.awt.EventDispatchThread.pumpEvents(EventDispatchThread.java:101)
at java.awt.EventDispatchThread.pumpEvents(EventDispatchThread.java:93)
at java.awt.EventDispatchThread.run(EventDispatchThread.java:82)

Here's my class:

 import java.awt.BorderLayout;
 import java.awt.event.ActionEvent;
 import java.awt.event.ActionListener;
 import javax.swing.JButton;
 import javax.swing.JFrame;
 import javax.swing.JLabel;
 import javax.swing.JPanel;
 import javax.swing.SwingUtilities;
 import javax.swing.Timer;

 public class TwoPerson  extends JFrame{

    Timer timer;
    int counter = 0;

    public TwoPerson(){
        JFrame frame = new JFrame("Goddard Test Timer");
        frame.setDefaultCloseOperation(EXIT_ON_CLOSE);


        JButton button2 = new JButton("Restart");
        button2.addActionListener(new ActionListener(){
              public void actionPerformed(ActionEvent e) { 
              counter = 0;
              } 
            });

        JButton button1 = new JButton("Stop");
        button1.addActionListener(new ActionListener(){
              public void actionPerformed(ActionEvent e) { 
                  timer.stop();
              } 
            });

        JLabel label = new JLabel();
        JPanel jp = new JPanel();
        jp.add(label, BorderLayout.NORTH);
        jp.add(button1);
        jp.add(button2);

        frame.getContentPane().add(jp);
        frame.pack();
        frame.setVisible(true);
        frame.setSize(500, 500);

        final Timer timer = new Timer(1000, null);
       timer.addActionListener(new ActionListener() {
           public void actionPerformed(ActionEvent e) {

           label.setText(String.valueOf(counter));
        counter++;
        if (counter == 10){
        //Do stuff at certain times
                }
           }
       });
      timer.start();
    }

    public static void main(String[] args){
        SwingUtilities.invokeLater(new Runnable() {
        @Override
        public void run() {
        new TwoPerson();    
        }
        });
    }

}