How to "Refresh" the Java application

Question

I have made a time stamp that will display the current time. The following code are in the MyFrame Class. But I want to refresh the time stamp so that it can continuously display the current time every second. How can I do this? Thank you.
void jTime_actionPerformed(ActionEvent e) {
        date.time();
        date.setTimeStamp(jTimeLabel);These are the methods in the ClsDate Class.
public void time()
    GregorianCalendar calendar = new GregorianCalendar();
    Hour = +calendar.get(calendar.HOUR);
    Minute = +calendar.get(calendar.MINUTE);
    Second = +calendar.get(calendar.SECOND);
  public void setTimeStamp(JLabel T4)
    T4.setText(toString());
  public String toString()
    return (Hour + ":" + Minute + ":" + Second);
  }

Answer 1

import java.awt.*;
import java.awt.event.*;
import java.text.*;
import java.util.Date;
import javax.swing.*;
public class TimerExample implements Runnable {
    private JLabel timeLabel;
    private ActionListener al = new ActionListener() {
        DateFormat df = new SimpleDateFormat("HH:mm:ss");
        public void actionPerformed(ActionEvent evt) {
            timeLabel.setText(df.format(new Date()));
    @Override public void run() {
        timeLabel = new JLabel("__:__:__");
        new Timer(1000, al).start();
        JFrame f = new JFrame();
        f.getContentPane().add(timeLabel);
        f.pack();
        f.setDefaultCloseOperation(WindowConstants.EXIT_ON_CLOSE);
        f.setLocationRelativeTo(null);
        f.setVisible(true);
    public static void main(String[] args) {
        EventQueue.invokeLater(new TimerExample());
}