Demonstrate concurrency using timer.

concurrency.java

package supercat1;

import java.awt.*;
import java.awt.event.*;
import javax.swing.*; // Using Swing components and containers
import java.util.Timer
// A Swing application extends javax.swing.JFrame
public class supercat1 extends JFrame {
private JTextField tfCount;
// Use Swing's JTextField instead of AWT's TextField
private int count = 0;

//The TimerTask code is executed every second and the tfCount text field is updated depending on the value of mState.

//declare different states of the updater
private final int GOING_UP = 1;
private final int GOING_DOWN = 2;
private final int STOP = 3;

private int mState = STOP; //default state is stop

private Timer mTimer = new Timer();
private TimerTask mTask = new TimerTask() {
            @Override
            public void run() {
                SwingUtilities.invokeLater(new Runnable() {
                    @Override
                    public void run() {
                        //should use a switch statement
                        if (mState == GOING_UP){
                            ++count;
                        }else if(mState == GOING_DOWN){
                            --count;
                        }
                        tfCount.setText("" + count);
                    }
                });
            }
        }

public supercat1 () {
// Get the content pane of top-level container Jframe
// Components are added onto content pane
Container cp = getContentPane();
cp.setLayout(new FlowLayout());

cp.add(new JLabel("Counter"wink);
tfCount = new JTextField(count + "", 10);
tfCount.setEditable(false);
tfCount.setHorizontalAlignment(JTextField.RIGHT);
cp.add(tfCount);

JButton btnCount = new JButton("Count Up" ) ;
cp.add(btnCount);

JButton btnCountd = new JButton("Count Down" ) ;
cp.add(btnCountd);

JButton btnCounts = new JButton("Stop" ) ;
cp.add(btnCounts);
btnCount.addActionListener(new ActionListener() {
@Override
public void actionPerformed(ActionEvent e) {
    mState = GOING_UP;
    if (mState == STOP){//if it was previously stopped, start it
        mTimer.schedule(mTask, 1000, 1000)//execute mTask every second
    }
}

});

setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
// Exit program if Jframe's close-window button clicked
setSize(300, 100);
setTitle("Supercat Counter" );
setVisible(true); // show it
}

public static void main(String[] args) {
// Recommended to run the GUI construction in
// Event Dispatching thread for thread-safet operations
SwingUtilities.invokeLater(new Runnable() {
@Override
public void run() {
new supercat1(); // Let the constructor does the job
}
});
}
}