Digital Clock

1. Class Window

2. Source Code
NumberDisplay Class

/**
 * NumberDisplay Class
 *
 * @author (Arino Jenynof)
 * @version (20180929)
 */
public class NumberDisplay
{
    private int limit; //Upper bound, exclusive
    private int value; //Current value
    
    public NumberDisplay(int limit)
    {
        this.limit = limit;
        value = 0;
    }
    
    public int get_value()
    {
        return value;
    }
    
    public void set_value(int new_value)
    {
        if (new_value >= 0 && new_value < limit)
        {
            value = new_value;
        }
    }
    
    public String get_display()
    {
        if (value < 10)
        {
            return "0" + value;
        }
        else
        {
            return "" + value;
        }
    }
    
    public void increment()
    {
        value = (value + 1) % limit;
    }
}

PeriodDisplay Class

/**
 * PeriodDisplay Class
 *
 * @author (Arino Jenynof)
 * @version (20180929)
 */
public class PeriodDisplay
{
    private String period; //AM or PM
    
    public PeriodDisplay()
    {
        period = "AM";
    }
    
    public PeriodDisplay(String period)
    {
        this.period = period;
    }
    
    public String get_period()
    {
        return period;
    }
    
    public void set_period(String period)
    {
        this.period = period;
    }
}

ClockDisplay Class

/**
 * ClockDisplay Class
 *
 * @author (Arino Jenynof)
 * @version (20180929)
 */
public class ClockDisplay
{
    private NumberDisplay hours;
    private NumberDisplay minutes;
    private PeriodDisplay period;
    private String display; //For displaying current time
    
    /**
     * Constructor without initial input, set the clock to 00:00 AM
     */
    public ClockDisplay()
    {
        hours = new NumberDisplay(13); //12-Hour clock
        minutes = new NumberDisplay(60);
        period = new PeriodDisplay();
        update_display();
    }
    
    /**
     * Constructor with user input, set the clock according to user needs
     */
    public ClockDisplay(int hours, int minutes, String period)
    {
        this.hours = new NumberDisplay(13);
        this.minutes = new NumberDisplay(60);
        this.period = new PeriodDisplay();
        set_display(hours, minutes, period);
    }
    
    /**
     * Update display string
     */
    public void update_display()
    {
        display = hours.get_display() + ":" + minutes.get_display() + " " + period.get_period();;
    }
    
    public void set_display(int hours, int minutes, String period)
    {
        this.hours.set_value(hours);
        this.minutes.set_value(minutes);
        this.period.set_period(period);
        update_display();
    }
    
    public String get_display()
    {
        return display;
    }
    
    /**
     * Increment minute
     */
    public void tick()
    {
        minutes.increment();
        if (minutes.get_value() == 0)
        {
            hours.increment();
        }
        if (hours.get_value() == 12 && minutes.get_value() == 0)
        {
            if (period.get_period().equalsIgnoreCase("AM"))
            {
                period.set_period("PM");
            }
            else
            {
                period.set_period("AM");
            }
        }
        update_display();
    }
}

3. 12-Hour Clock

/**
 * 12-Hour Clock Demonstration
 *
 * @author (Arino Jenynof)
 * @version (20180929)
 */
public class Clock12Hour
{
    public void demo()
    {
        System.out.println("12-Hour Clock Demonstration");
        ClockDisplay clock = new ClockDisplay();
        clock.set_display(11, 55, "AM");
        System.out.println(clock.get_display());
        
        int i = 10;
        while (i > 0)
        {
            clock.tick();
            System.out.println(clock.get_display());
            i--;
        }
    }
}

Output

3. 12-Hour Clock with GUI

/**
 * ClockGUI Class
 * Displaying Clock with GUI
 *
 * @author (Arino Jenynof)
 * @version (20180929)
 */
import java.awt.*;
import java.awt.event.*;
import javax.swing.*;
import javax.swing.border.*;
public class ClockGUI
{
    private JFrame frame;
    private JLabel label;
    private ClockDisplay clock;
    private boolean clockRunning = false;
    private TimerThread timerThread;
    
    public ClockGUI()
    {
        clock = new ClockDisplay();
        makeFrame();
    }
    
    public ClockGUI(int hours, int minute, String period)
    {
        clock = new ClockDisplay(hours, minute, period);
        makeFrame();
    }
    
    private void start()
    {
        clockRunning = true;
        timerThread = new TimerThread();
        timerThread.start();
    }
    
    private void stop()
    {
        clockRunning = false;
    }
    
    private void step()
    {
        clock.tick();
        label.setText(clock.get_display());
    }
    
    private void showAbout()
    {
        JOptionPane.showMessageDialog(frame,
            "Clock v1.0\n" +
            "A simple interface for the 'Object First' clock display project",
            "About Clock",
            JOptionPane.INFORMATION_MESSAGE);
    }
    
    private void quit()
    {
        System.exit(0);
    }
    
    private void makeMenuBar(JFrame frame)
    {
        final int SHORTCUT_MASK = Toolkit.getDefaultToolkit().getMenuShortcutKeyMask();
        JMenuBar menubar = new JMenuBar();
        frame.setJMenuBar(menubar);
        JMenu menu;
        JMenuItem item;
        
        menu = new JMenu("File");
        menubar.add(menu);
        
        item = new JMenuItem("About Clock. . . ");
        item.addActionListener(e->showAbout());
        menu.add(item);
        
        menu.addSeparator();
        
        item = new JMenuItem("Quit");
        item.setAccelerator(KeyStroke.getKeyStroke(KeyEvent.VK_Q, SHORTCUT_MASK));
        item.addActionListener(e->quit());
        menu.add(item);
    }
    
    private void makeFrame()
    {
        frame = new JFrame("Clock");
        JPanel contentPane = (JPanel)frame.getContentPane();
        contentPane.setBorder(new EmptyBorder(1, 60, 1, 60));
        makeMenuBar(frame);
        
        contentPane.setLayout(new BorderLayout(50, 50));
        
        label = new JLabel(clock.get_display(), SwingConstants.CENTER);
        Font displayFont = label.getFont().deriveFont(96.0f);
        label.setFont(displayFont);
        contentPane.add(label, BorderLayout.CENTER);
        
        JPanel toolbar = new JPanel();
        toolbar.setLayout(new GridLayout(1, 0));
        
        JButton startButton = new JButton("Start");
        startButton.addActionListener(e->start());
        toolbar.add(startButton);
        
        JButton stopButton = new JButton("Stop");
        stopButton.addActionListener(e->stop());
        toolbar.add(stopButton);
        
        JButton stepButton = new JButton("Step");
        stepButton.addActionListener(e->step());
        toolbar.add(stepButton);
        
        JPanel flow = new JPanel();
        flow.add(toolbar);
        contentPane.add(flow, BorderLayout.SOUTH);
        
        frame.pack();
        
        Dimension d = Toolkit.getDefaultToolkit().getScreenSize();
        frame.setLocation(d.width/2 - frame.getWidth()/2, d.height/2 - frame.getHeight()/2);
        frame.setVisible(true);
    }
    
    public class TimerThread extends Thread
    {
        public void run()
        {
            while (clockRunning)
            {
                step();
                pause();
            }
        }
        
        private void pause()
        {
            try
            {
                Thread.sleep(1000);
            }
            catch (InterruptedException exc)
            {
                //NOP
            }
        }
    }
}

Output