import java.awt.Dimension;

import java.text.SimpleDateFormat;

import java.util.Calendar;

import java.util.Date;

import java.util.Timer;

import java.util.TimerTask;

import javax.swing.JFrame;

import javax.swing.JLabel;

import javax.swing.JPanel;

//第一种比较推荐：

public class TimeFrame extends JFrame

{

 /*

 * Variables

 */

 private JPanel timePanel;

 private JLabel timeLabel;

 private JLabel displayArea;

 private String DEFAULT_TIME_FORMAT = "HH:mm:ss";

 private String time;

 private int ONE_SECOND = 1000;

 public TimeFrame()

 {

 timePanel = new JPanel();

 timeLabel = new JLabel("CurrentTime: ");

 displayArea = new JLabel();

 configTimeArea();

 timePanel.add(timeLabel);

 timePanel.add(displayArea);

 this.add(timePanel);

 this.setDefaultCloseOperation(EXIT_ON_CLOSE);

 this.setSize(new Dimension(200,70));

 this.setLocationRelativeTo(null);

 }

 /**

 * This method creates a timer task to update the time per second

 */

 private void configTimeArea() {

 Timer tmr = new Timer();

 tmr.scheduleAtFixedRate(new JLabelTimerTask(),new Date(), ONE_SECOND);

 }

 /**

 * Timer task to update the time display area

 *

 */

 protected class JLabelTimerTask extends TimerTask{

 SimpleDateFormat dateFormatter = new SimpleDateFormat(DEFAULT_TIME_FORMAT);

 @Override

 public void run() {

  time = dateFormatter.format(Calendar.getInstance().getTime());

  displayArea.setText(time);

 }

 }

 public static void main(String arg[])

 {

 TimeFrame timeFrame=new TimeFrame();

 timeFrame.setVisible(true);

 }

}

import java.awt.Dimension;

import java.text.SimpleDateFormat;

import java.util.Calendar;

import javax.swing.JFrame;

import javax.swing.JLabel;

import javax.swing.JPanel;

//第二种

public class DTimeFrame2 extends JFrame implements Runnable{

	 private JFrame frame;

	 private JPanel timePanel;

	 private JLabel timeLabel;

	 private JLabel displayArea;

	 private String DEFAULT_TIME_FORMAT = "HH:mm:ss";

	 private int ONE_SECOND = 1000;

	 public DTimeFrame2()

	 {

	 timePanel = new JPanel();

	 timeLabel = new JLabel("CurrentTime: ");

	 displayArea = new JLabel();

	 timePanel.add(timeLabel);

	 timePanel.add(displayArea);

	 this.add(timePanel);

	 this.setDefaultCloseOperation(EXIT_ON_CLOSE);

	 this.setSize(new Dimension(200,70));

	 this.setLocationRelativeTo(null);

	 }

	 public void run()

	 {

	 while(true)

	 {

	  SimpleDateFormat dateFormatter = new SimpleDateFormat(DEFAULT_TIME_FORMAT);

	  displayArea.setText(dateFormatter.format(

	     Calendar.getInstance().getTime()));

	  try

	  {

	  Thread.sleep(ONE_SECOND);

	  }

	  catch(Exception e)

	  {

	  displayArea.setText("Error!!!");

	  }

	 }

	 } 

	 public static void main(String arg[])

	 {

	 DTimeFrame2 df2=new DTimeFrame2();

	 df2.setVisible(true);

	 Thread thread1=new Thread(df2);

	 thread1.start();

	 }

	}

import java.awt.BorderLayout;

import java.awt.event.ActionEvent;

import java.awt.event.ActionListener;

import java.text.SimpleDateFormat;

import java.util.Calendar;

import java.util.Date;

import java.util.Locale;

import java.util.TimeZone;

import java.util.Timer;

import java.util.TimerTask;

import javax.swing.DefaultComboBoxModel;

import javax.swing.JComboBox;

import javax.swing.JFrame;

import javax.swing.JLabel;

import javax.swing.JPanel;

//第三种：多国时钟实现

public class WorldTimeFrame extends JFrame

{

 /**

 *

 */

 private static final long serialVersionUID = 4782486524987801209L;

 private String time;

 private JPanel timePanel;

 private TimeZone timeZone;//时区

 private JComboBox zoneBox;

 private JLabel displayArea;

 private int ONE_SECOND = 1000;

 private String DEFAULT_FORMAT = "EEE d MMM, HH:mm:ss";

 public WorldTimeFrame()

 {

 zoneBox = new JComboBox();

 timePanel = new JPanel();

 displayArea = new JLabel();

 timeZone = TimeZone.getDefault();

 zoneBox.setModel(new DefaultComboBoxModel(TimeZone.getAvailableIDs()));

 zoneBox.addActionListener(new ActionListener(){

  @Override

  public void actionPerformed(ActionEvent e) {

  updateTimeZone(TimeZone.getTimeZone((String) zoneBox.getSelectedItem()));

  }

 });

 configTimeArea();

 timePanel.add(displayArea);

 this.setLayout(new BorderLayout());

 this.add(zoneBox, BorderLayout.NORTH);

 this.add(timePanel, BorderLayout.CENTER);

 this.setLocationRelativeTo(null);

 this.setDefaultCloseOperation(EXIT_ON_CLOSE);

 this.setVisible(true);

 pack();

 }

 /**

 * This method creates a timer task to update the time per second

 */

 private void configTimeArea() {

 Timer tmr = new Timer();

 tmr.scheduleAtFixedRate(new JLabelTimerTask(),new Date(), ONE_SECOND);

 }

 /**

 * Timer task to update the time display area

 *

 */

 public class JLabelTimerTask extends TimerTask{

 SimpleDateFormat dateFormatter = new SimpleDateFormat(DEFAULT_FORMAT, Locale.ENGLISH);

 @Override

 public void run() {

  dateFormatter.setTimeZone(timeZone);

  time = dateFormatter.format(Calendar.getInstance().getTime());

  displayArea.setText(time);

 }

 }

 /**

 * Update the timeZone

 * @param newZone

 */

 public void updateTimeZone(TimeZone newZone)

 {

 this.timeZone = newZone;

 }

 public static void main(String arg[])

 {

 new WorldTimeFrame();

 }

}