why does it always give the same time?

I used the following program to get the clock.What it turned out to be is a static clock ? Why is it so ?

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

class tester {

    JFrame fr = new JFrame();
    JPanel p = new JPanel();
    JLabel l = new JLabel();
    Date d = new Date();
    GregorianCalendar gc = new GregorianCalendar();

    tester() {

    public void startClockThread() {
        Runnable r = new Runnable() {
            public void run() {
        new Thread(r).start();

    public void startClock() {
        while(true) {
            l.setText(gc.get(gc.HOUR) + ":" + gc.get(gc.MINUTE) + ":" + gc.get(gc.SECOND));

    public static void main(String args[]) {
        new tester();


GregorianCalendar() Constructs a default GregorianCalendar using the current time in the default time zone with the default locale. Java Doc

You can do this way.

while(true) {
       GregorianCalendar gc = new GregorianCalendar();
   l.setText(gc.get(gc.HOUR) + ":" + gc.get(gc.MINUTE) + ":" + gc.get(gc.SECOND));

Now you should understand why you are getting a static clock !

You only create the GregorianCalendar once, and it never gets updated. So the date is always the same.

there's are big problems apart from the one you have spotted:

  • dont let threads run wild, they'll freeze the ui eventually
  • each and every access to a Swing component must happen on the EDT

You can solve both easiest by using a javax.swing.Timer

ActionListener nextSecond = new ActionListener() {
     public void actionPerformed(ActionEvent e) {
         // get time ...
new Timer(1000, nextSecond).start();

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