How to use Thread

Question

Hi,
I am trying to write a program that does a background process. The process is controlled by two buttons: Start and Stop. I thought I'd use threads, but it does not work; the start button remains depressed and the user cannot click on the Stop button. The line calling run() is executed and execution transfers to the run method in my Thread subclass, which is wrapped in an infinite loop. The line after the run() method is never reached. It is as if it is not creating an extra thread at all.
I have written something basic which is similar, the same problem occurs with this code:
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;
import javax.swing.JButton;
import javax.swing.JFrame;
import javax.swing.JPanel;
public class CounterFrame extends JFrame {
    private JPanel pnButtons;
    private JButton btStart;
    private JButton btStop; 
    private ThreadTester threadtester;
    public CounterFrame() {
        pnButtons = new JPanel();
        btStart = new JButton("Start");
        btStop = new JButton("Stop");
        btStart.addActionListener(new StartListener());
        btStop.addActionListener(new StopListener());   
        pnButtons.add(btStart);
        pnButtons.add(btStop);
        add(pnButtons);
        pack();
        threadtester = new ThreadTester();
    private class StartListener implements ActionListener {
        public void actionPerformed(ActionEvent e) {
            threadtester.run();
    private class StopListener implements ActionListener {
        public void actionPerformed(ActionEvent e) {
            try {
                threadtester.sleep(Long.MAX_VALUE);
            } catch (InterruptedException ex) {
                ex.printStackTrace();
    private class ThreadTester extends Thread {
        int counter;
        public ThreadTester() {
            counter = 0;
        public void run() {
            while(true) {
                System.out.println(counter);
                counter++;
                try {
                    sleep(1000);
                } catch (InterruptedException ex) {
                    ex.printStackTrace();
                yield();
    public static void main(String args[]) {
        java.awt.EventQueue.invokeLater(new Runnable() {
            public void run() {
                new CounterFrame().setVisible(true);
}Can anyone advise where I am going wrong, please?

Answer 1

Please run, don't walk to the article on the Sun site (you can search for it) entitled Concurrency and Swing (or something similar). Problems I see include:
1) Don't call run on a thread as that will just "run" the run method and not create a background thread. Instead you call "start".
2) Don't call Thread.sleep() on the EDT or the Event Dispatch Thread. This is the single thread that Swing uses to draw components and to interact with the user. Calling Thread.sleep on it will put your whole program to sleep which is not what you want.
3) Consider using a Swing Worker, or better still a Swing Timer.
Again, read the article and you will understand this better.