java :按鈕觸發定時器

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.JTextField;
import javax.swing.Timer;


public class Form_test {
private static String value;
static Timer timer;
public static void main(String[] args) {


JFrame frame = new JFrame("Communication with Arduino");
frame.setSize(350, 200);
frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
JPanel panel = new JPanel();
frame.add(panel);
placeComponents(panel);
frame.setVisible(true);
}


private static void placeComponents(JPanel panel) {
panel.setLayout(null);
JLabel userLabel = new JLabel("Set Serial Port:");
userLabel.setBounds(50, 40, 110, 25);
panel.add(userLabel);


JTextField userset = new JTextField(20);
userset.setBounds(170, 40, 110, 25);
panel.add(userset);


JButton start = new JButton("Start");
start.setBounds(70, 100, 80, 25);
panel.add(start);
start.addActionListener(new ActionListener() {          //爲start按鈕添加點擊事件

@Override
public void actionPerformed(ActionEvent e) {
// TODO Auto-generated method stub
value = userset.getText();
    timer = new Timer(1000, new ActionListener() {         //添加一個定時器
           public void actionPerformed(ActionEvent e) {
new Thread(new Runnable() {                 //定時器裏啓動一個線程
@Override
public void run() {
// TODO Auto-generated method stub
System.out.println(value);
}
}).start();
           }      
       });
       timer.start();                                                                  //開啓定時器
}
});
JButton stop = new JButton("stop");
stop.setBounds(190, 100, 80, 25);
panel.add(stop);
stop.addActionListener(new ActionListener(){
@Override
public void actionPerformed(ActionEvent e) {
// TODO Auto-generated method stub
timer.stop();                                                         //啓動定時器
}});
}
}