Chapter 30 Exercise 7, Introduction to Java Programming, Tenth Edition Y. Daniel LiangY.

30.7 (Control a clock) Rewrite Programming Exercise 15.32 using a thread to control the clock animation.

import java.awt.*;
import java.awt.event.*;
import java.util.Calendar;
import java.util.GregorianCalendar;

import javax.swing.*;

public class Exercise07 extends JApplet {
 private ClockPanel clockPanel1 = new ClockPanel();
 private ClockPanel clockPanel2 = new ClockPanel();
 private ClockPanel clockPanel3 = new ClockPanel(); 
 private static final long serialVersionUID = 1L;
 
 public static void main(String[] args) {
  Exercise07 applet = new Exercise07();
  JFrame frame = new JFrame();
  frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
  frame.setTitle("Exercise07");
  frame.add(applet, BorderLayout.CENTER);
  frame.setSize(900, 400);
  frame.setLocationRelativeTo(null);
  frame.setVisible(true);
 }
 
 public Exercise07() {
  JPanel panel1 = new JPanel(new GridLayout(1, 3));
  panel1.add(clockPanel1);
  panel1.add(clockPanel2);
  panel1.add(clockPanel3);
  add(panel1, BorderLayout.CENTER);
  JPanel panel2 = new JPanel();
  JButton jButton1 = new JButton("Resume All");
  JButton jButton2 = new JButton("Suspend All");
  jButton1.addActionListener(new ActionListener() {   
   @Override
   public void actionPerformed(ActionEvent e) {
    clockPanel1.start();
    clockPanel2.start();
    clockPanel3.start();
   }
  });
  jButton2.addActionListener(new ActionListener() {   
   @Override
   public void actionPerformed(ActionEvent e) {
    clockPanel1.stop();
    clockPanel2.stop();
    clockPanel3.stop();
   }
  });
  panel2.add(jButton2);
  panel2.add(jButton1);
  add(panel2, BorderLayout.SOUTH);
 }

 class ClockPanel extends JPanel implements Runnable {
  private JButton jbtStart = new JButton("Resume");
  private JButton jbtStop = new JButton("Suspend");
  private boolean isRunning = true;
  private static final long serialVersionUID = 1L;
  private StillClock clock = new StillClock();
  
  public void stop() {
   isRunning = false;
  }
  
  public void start() {
   isRunning = true;
  }
  
  public ClockPanel() {
   setLayout(new BorderLayout());
   JPanel panel1 = new JPanel();
   jbtStop.addActionListener(new ActionListener() {   
    @Override
    public void actionPerformed(ActionEvent e) {
     isRunning = false;
    }
   } );
   panel1.add(jbtStop);
   jbtStart.addActionListener(new ActionListener() {   
    @Override
    public void actionPerformed(ActionEvent e) {
     isRunning = true;    
    }
   } );  
   panel1.add(jbtStart);
   add(panel1, BorderLayout.SOUTH);
   add(clock, BorderLayout.CENTER);
   Thread thread = new Thread(this);
   thread.start();
  }
 
  @Override
  public void run() {
   try {
    while (true) {
     Thread.sleep(1000); 
     if(isRunning) {
      clock.setCurrentTime();
      clock.repaint();      
     }
    }    
   } catch (InterruptedException e) {
    e.printStackTrace();
   }
  }
 }
 
 class StillClock extends JPanel {
  private static final long serialVersionUID = 1L;
  private int hour;
  private int minute;
  private int second;

  /** Construct a default clock with the current time */
  public StillClock() {
   setCurrentTime();
  }

  /** Construct a clock with specified hour, minute, and second */
  public StillClock(int hour, int minute, int second) {
   this.hour = hour;
   this.minute = minute;
   this.second = second;
  }

  /** Return hour */
  public int getHour() {
   return hour;
  }

  /** Set a new hour */
  public void setHour(int hour) {
   this.hour = hour;
   repaint();
  }

  /** Return minute */
  public int getMinute() {
   return minute;
  }

  /** Set a new minute */
  public void setMinute(int minute) {
   this.minute = minute;
   repaint();
  }

  /** Return second */
  public int getSecond() {
   return second;
  }

  /** Set a new second */
  public void setSecond(int second) {
   this.second = second;
   repaint();
  }

  @Override
  /** Draw the clock */
  protected void paintComponent(Graphics g) {
   super.paintComponent(g);

   // Initialize clock parameters
   int clockRadius = (int) (Math.min(getWidth(), getHeight()) * 0.8 * 0.5);
   int xCenter = getWidth() / 2;
   int yCenter = getHeight() / 2;

   // Draw circle
   g.setColor(Color.black);
   g.drawOval(xCenter - clockRadius, yCenter - clockRadius,
     2 * clockRadius, 2 * clockRadius);
   g.drawString("12", xCenter - 5, yCenter - clockRadius + 12);
   g.drawString("9", xCenter - clockRadius + 3, yCenter + 5);
   g.drawString("3", xCenter + clockRadius - 10, yCenter + 3);
   g.drawString("6", xCenter - 3, yCenter + clockRadius - 3);

   // Draw second hand
   int sLength = (int) (clockRadius * 0.8);
   int xSecond = (int) (xCenter + sLength
     * Math.sin(second * (2 * Math.PI / 60)));
   int ySecond = (int) (yCenter - sLength
     * Math.cos(second * (2 * Math.PI / 60)));
   g.setColor(Color.red);
   g.drawLine(xCenter, yCenter, xSecond, ySecond);

   // Draw minute hand
   int mLength = (int) (clockRadius * 0.65);
   int xMinute = (int) (xCenter + mLength
     * Math.sin(minute * (2 * Math.PI / 60)));
   int yMinute = (int) (yCenter - mLength
     * Math.cos(minute * (2 * Math.PI / 60)));
   g.setColor(Color.blue);
   g.drawLine(xCenter, yCenter, xMinute, yMinute);

   // Draw hour hand
   int hLength = (int) (clockRadius * 0.5);
   int xHour = (int) (xCenter + hLength
     * Math.sin((hour % 12 + minute / 60.0) * (2 * Math.PI / 12)));
   int yHour = (int) (yCenter - hLength
     * Math.cos((hour % 12 + minute / 60.0) * (2 * Math.PI / 12)));
   g.setColor(Color.green);
   g.drawLine(xCenter, yCenter, xHour, yHour);
  }

  public void setCurrentTime() {
   // Construct a calendar for the current date and time
   Calendar calendar = new GregorianCalendar();

   // Set current hour, minute and second
   this.hour = calendar.get(Calendar.HOUR_OF_DAY);
   this.minute = calendar.get(Calendar.MINUTE);
   this.second = calendar.get(Calendar.SECOND);
  }

  @Override
  public Dimension getPreferredSize() {
   return new Dimension(200, 200);
  }
 }

}