Java Source - Tạo đồng hồ điện tử đơn giản(Make simple digital clock).

Đoạn source sau sẽ tạo một đồng hồ điện tử đơn giản trên Java JFrame(simple digital clock).

Bên dưới là toàn bộ mã nguồn:

import javax.swing.*; 
import java.awt.*; 
import java.util.Date; 
 
public class SimpleDigitalClock extends JPanel 
{ 
    JFrame frame; 
 
    int currentHour; 
    int currentMinute; 
    int currentSecond; 
 
    //Font that will be use to show digital clock 
    Font myFont=new Font("Tahoma",Font.BOLD+Font.ITALIC,20); 
 
    //Color that will be use to show digital clock 
    Color myColor=new Color(255,0,0); 
 
    //Font metrics that will use to store font informations 
    //For example, width of a character 
    FontMetrics fm; 
 
    public SimpleDigitalClock() 
    { 
        //Create a window using JFrame with title ( Simple Digital Clock ) 
        frame=new JFrame("Simple Digital Clock"); 
 
        //add(this) mean add created panel into JFrame 
        //Which panel ? 
        //See line 81 and 7 (I hope you understand it) 
        frame.add(this); 
 
        //Set default close operation for JFrame 
        frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE); 
 
        //Set JFrame size 
        frame.setSize(300,300); 
 
        //Make JFrame locate at center 
        frame.setLocationRelativeTo(null); 
 
        //Make JFrame visible 
        frame.setVisible(true); 
 
        /*
        *Loop that will make sure panel show current time
        *like current second, current minute and current hour.
        */ 
        while(true) 
        { 
            //It will do all code in method paint(See line 67) 
            repaint(); 
 
            try 
            { 
                Thread.sleep(900); 
            } 
            catch(Exception exception) 
            { 
                exception.printStackTrace(); 
            } 
        } 
    } 
 
    public void paint(Graphics g) 
    { 
        super.paint(g); 
 
        /*
        *Create  current Date object. It means it store information
        *about current hour, minute and second.
        */ 
        Date myDate=new Date(); 
 
        currentHour=myDate.getHours(); 
        currentMinute=myDate.getMinutes(); 
        currentSecond=myDate.getSeconds(); 
 
        //Set font that will use to draw digital number 
        g.setFont(myFont); 
 
        //Information about distance between number in digital clock 
        fm=g.getFontMetrics(); 
        int hourXCoordinate=20; 
        int minuteXCoordinate=hourXCoordinate+(fm.getMaxAdvance()*2); 
        int secondXCoordinate=hourXCoordinate+(fm.getMaxAdvance()*4); 
 
        //Set color that will use to draw digital number 
        g.setColor(myColor); 
 
        //Draw hour, draw (:) between number, draw minute and draw second. 
        g.drawString(Integer.toString(currentHour),hourXCoordinate,20); 
        g.drawString(":",(hourXCoordinate+minuteXCoordinate)/2,20); 
        g.drawString(Integer.toString(currentMinute),minuteXCoordinate,20); 
        g.drawString(":",(secondXCoordinate+minuteXCoordinate)/2,20); 
        g.drawString(Integer.toString(currentSecond),secondXCoordinate,20); 
    } 
 
    public static void main(String[]args) 
    { 
        SimpleDigitalClock sdc=new SimpleDigitalClock(); 
    }
   
}