// An analog clock -- Using Timer and Calendar.
// Uses a BufferedImage and antialiasing.
// The second hand creep is from the Timer, which seems to take
// a little longer than the requested time to call the listener.
// -- Fred Swartz, 1 May 1999, 2002-02-21 from applet to application

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

///////////////////////////////////////////////////////////// ClockAnalogBuf
public class ClockAnalogBuf extends JFrame {

Clock clockFace;

//================================================================= main
public static void main(String[] args) {
JFrame windo = new ClockAnalogBuf();
windo.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
windo.setVisible(true);
}//end main

//========================================================== constructor
public ClockAnalogBuf() {
Container content = this.getContentPane();
content.setLayout(new BorderLayout());
clockFace = new Clock();
content.add(clockFace, BorderLayout.CENTER);

this.setTitle("Analog Clock");
this.pack();

clockFace.start();
}//end constructor
}//end class ClockAnalogBuf

//////////////////////////////////////////////////////////////// Clock class
class Clock extends JPanel {

private int hours = 0;
private int minutes = 0;
private int seconds = 0;
private int millis = 0;

private static final int spacing = 10;
private static final float twoPi = (float)(2.0 * Math.PI);
private static final float threePi = (float)(3.0 * Math.PI);
// Angles for the trigonometric functions are measured in radians.
// The following in the number of radians per sec or min.
private static final float radPerSecMin = (float)(Math.PI / 30.0);

private int size; // height and width of clock face
private int centerX; // x coord of middle of clock
private int centerY; // y coord of middle of clock
private BufferedImage clockImage;
private javax.swing.Timer t;

//==================================================== Clock constructor
public Clock() {
this.setPreferredSize(new Dimension(300,300));
this.setBackground(Color.white);
this.setForeground(Color.black);

t = new javax.swing.Timer(1000,
new ActionListener() {
public void actionPerformed(ActionEvent e) {
update();
}
});
}//end constructor

//=============================================================== update
// Replace the default update so that the plain background
// doesn't get drawn.
public void update() {
// Hmmm, is this the right way to do this? Or do we just
// call paintComponent? Does this coalesce calls, not that
// this updates often enuf for that to be important.
this.repaint();
}//end update

//================================================================ start
public void start() {
t.start(); // start the timer
}//end start

//================================================================= stop
public void stop() {
t.stop(); // start the timer
}//end stop

//======================================================= paintComponent

public void paintComponent(Graphics g) {
super.paintComponent(g); // paint background, borders
Graphics2D g2 = (Graphics2D)g;
g2.setRenderingHint(RenderingHints.KEY_ANTIALIASING,
RenderingHints.VALUE_ANTIALIAS_ON);

// The panel may have been resized, get current dimensions
int w = getWidth();
int h = getHeight();
size = ((w<h) ? w : h) - 2*spacing;
centerX = size/2 + spacing;
centerY = size/2 + spacing;

// Create the clock face background image if this is the first time,
// or if the size of the panel has changed
if (clockImage == null
|| clockImage.getWidth() != w
|| clockImage.getHeight() != h) {

clockImage = (BufferedImage)(this.createImage(w, h));
// now get a graphics context from this image
Graphics2D gc = clockImage.createGraphics();
gc.setRenderingHint(RenderingHints.KEY_ANTIALIASING,
RenderingHints.VALUE_ANTIALIAS_ON);
drawClockFace(gc);
}

// Now get the time and draw the hands.
Calendar now = Calendar.getInstance();
hours = now.get(Calendar.HOUR);
minutes = now.get(Calendar.MINUTE);
seconds = now.get(Calendar.SECOND);
millis = now.get(Calendar.MILLISECOND);

// Draw the clock face from the precomputed image
g2.drawImage(clockImage, null, 0, 0);

// Draw the clock hands
drawClockHands(g);
}//end paintComponent

//======================================================= drawClockHands
private void drawClockHands(Graphics g) {
int secondRadius = size/2;
int minuteRadius = secondRadius * 3/4;
int hourRadius = secondRadius/2;

// second hand
float fseconds = seconds + (float)millis/1000;
float secondAngle = threePi - (radPerSecMin * fseconds);
drawRadius(g, centerX, centerY, secondAngle, 0, secondRadius);

// minute hand
float fminutes = (float)(minutes + fseconds/60.0);
float minuteAngle = threePi - (radPerSecMin * fminutes);
drawRadius(g, centerX, centerY, minuteAngle, 0, minuteRadius);

// hour hand
float fhours = (float)(hours + fminutes/60.0);
float hourAngle = threePi - (5 * radPerSecMin * fhours);
drawRadius(g, centerX, centerY, hourAngle, 0, hourRadius);
}//end drawClockHands

//======================================================== drawClockFace
private void drawClockFace(Graphics g) {
// clock face
g.setColor(Color.pink);
g.fillOval(spacing, spacing, size, size);
g.setColor(Color.black);
g.drawOval(spacing, spacing, size, size);

// tic marks
for (int sec = 0; sec<60; sec++) {
int ticStart;
if (sec%5 == 0) {
ticStart = size/2-10;
} else {
ticStart = size/2-5;
}
drawRadius(g, centerX, centerY, radPerSecMin*sec, ticStart , size/2);
}
}//endmethod drawClockFace

//=========================================================== drawRadius
private void drawRadius(Graphics g, int x, int y, double angle,
int minRadius, int maxRadius) {
float sine = (float)Math.sin(angle);
float cosine = (float)Math.cos(angle);

int dxmin = (int)(minRadius * sine);
int dymin = (int)(minRadius * cosine);

int dxmax = (int)(maxRadius * sine);
int dymax = (int)(maxRadius * cosine);
g.drawLine(x+dxmin, y+dymin, x+dxmax, y+dymax);
}//end drawRadius

}//endclass Clock