摆动数字时钟的示例

import javax.swing.*;
import java.awt.*;
import java.text.*;
import java.util.*;
public class DigitalWatch implements Runnable{
JFrame f;
Thread t=null;
int hours=0, minutes=0, seconds=0;
String timeString = "";
JButton b;

DigitalWatch(){
	f=new JFrame();
	
	t = new Thread(this);
        t.start();
	
	b=new JButton();
        b.setBounds(100, 100, 100, 50);
	
	f.add(b);
	f.setSize(300, 400);
	f.setLayout(null);
	f.setVisible(true);
}

 public void run() {
      try {
         while (true) {

            Calendar cal = Calendar.getInstance();
            hours = cal.get( Calendar.HOUR_OF_DAY );
            if ( hours > 12 ) hours -= 12;
            minutes = cal.get( Calendar.MINUTE );
            seconds = cal.get( Calendar.SECOND );

            SimpleDateFormat formatter = new SimpleDateFormat("hh:mm:ss");
            Date date = cal.getTime();
            timeString = formatter.format( date );

            printTime();

            t.sleep( 1000 );  // interval given in milliseconds
         }
      }
      catch (Exception e) { }
 }

public void printTime(){
b.setText(timeString);
}

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

}
}