TThread3.java

import javax.swing.*;
import java.awt.*;
import java.awt.event.*;

public class TThread3 extends JFrame {
    Counter ctr = null;
    JButton btnStart, btnStop;
    JLabel lblNum;
    int count = 0;
    boolean running = false;

private class Counter extends Thread {
        public void run() {
            while (count++ < 10000) {
                if (!running) break;
                lblNum.setText(Integer.toString(count));
                try {
                    sleep(100);
                } catch (InterruptedException e) {
                    System.out.println("Application Interrupted");
                }
            }
        }
    }

public static void main(String[] args) {
        TThread3 app = new TThread3();
        app.addWindowListener(new WindowAdapter() {
            public void windowClosing(WindowEvent e) {
                System.exit(0);
            }
        });
        app.init();
        app.pack();
        app.setVisible(true);
    }

public void init() {
        Container c = this.getContentPane();
        c.setLayout(new GridLayout(3,1));
        lblNum = new JLabel("Running Total");
        btnStart = new JButton("Start");
        btnStop = new JButton("Stop");
        btnStop.setEnabled(false);

btnStart.addActionListener(new ActionListener() {
            public void actionPerformed(ActionEvent e) {
                btnStart.setEnabled(false);
                btnStop.setEnabled(true);
                running = true;
                ctr = new Counter();
                ctr.start();
            }
        });

btnStop.addActionListener(new ActionListener() {
            public void actionPerformed(ActionEvent e) {
                if (ctr != null) {
                    running = false;
                    btnStart.setEnabled(true);
                    btnStop.setEnabled(false);
                }
            }
        });

c.add(lblNum);
        c.add(btnStart);
        c.add(btnStop);
    }
}