Digital clock by using Java

7:53 PM No Comments

Here is a piece of code to build a Java clock, that uses threads, gets the data for time automatically and is not interrupted if you click something else on the window. There are some comments around the code to help you understand what's happening.

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

class Clock extends JFrame implements Runnable
{
  Thread runner; //declare global objects
  Font clockFont;

     public Clock()
     {
       super("Java clock");
       setSize( 350, 100);
       setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
       setVisible(true);
       setResizable(false);                             //create window
  
       clockFont = new Font("Serif", Font.BOLD, 40);    //create font instance
      
       Container contentArea = getContentPane();
       ClockPanel timeDisplay = new ClockPanel();


       contentArea.add(timeDisplay);                    //add components
       setContentPane(contentArea);
       start();                                         //start thread running
    
     }
        
     class ClockPanel extends JPanel
     {
      public void paintComponent(Graphics painter )
        {
        Image pic =
          Toolkit.getDefaultToolkit().getImage("background.jpg");
        
         if(pic != null)
          
            painter.drawImage(pic, 0, 0, this);     //create image
                     
//if I didn't use a background image I would have used the setColor and fillRect methods to set background
    
          painter.setFont(clockFont);                   //create clock components
          painter.setColor(Color.black);
          painter.drawString( timeNow(), 60, 40);
        }
     }
    
     //get current time
     public String timeNow()
     {
       Calendar now = Calendar.getInstance();
       int hrs = now.get(Calendar.HOUR_OF_DAY);
       int min = now.get(Calendar.MINUTE);
       int sec = now.get(Calendar.SECOND);
      
       String time = zero(hrs)+":"+zero(min)+":"+zero(sec);
      
       return time;
     }
   
     public String zero(int num)
     {
       String number=( num < 10) ? ("0"+num) : (""+num);
       return number;                                    //Add leading zero if needed
      
     }
         
     public void start()
     {
       if(runner == null) runner = new Thread(this);
       runner.start();                                  //method to start thread
     }


     public void run()
     {
       while (runner == Thread.currentThread() )
       {
        repaint();
                                                         //define thread task
           try
             {
               Thread.sleep(1000);
             }
              catch(InterruptedException e)
                  {
                    System.out.println("Thread failed");
                  }                
       }
     }
    
     //create main method
     public static void main(String [] args)
     {
       Clock eg = new Clock();
     }
}