Draw Pie Chart in Java Swings

This Java Pie Chart example is going to show you how to draw Pie Charts in Java.

This Java Pie Chart example is drawing a pie chart to show the percentage of marks obtained in particular session. In this example we have used the object of JFrame class that calls the PieChartPanel class. The Font class represents the font 'Book Antiqua'.

The method getPercentInstance() of NumberFormat class returns the percentage format for the current default locale. The ComponenetAdapter class is an abstract adapter class which is called to receive the component events. The BufferedImage class is called by image = new BufferedImage(width, height, BufferedImage.TYPE_INT_RGB) which defines the image of pie chart The method Math.min(width,height) returns the smaller of two into values. The Ellipse2D.Double class is called to draw the circle shape.

Following code draws the leading edge of pie:
g2.draw(new Line2D.Double(cp, cq, p, q))

The angle is defined by:
phi = (marks[j]/total) * 2 * Math.PI

Following code marks the center on centerline:
p = cp + (9*pie/24) * Math.cos(theta + phi/2);
q = cq + (9*pie/24) * Math.sin(theta + phi/2);

FontRenderContext class is used to measure the text.

Following code shows the percent values outside the circle:
s = nf.format(data[j]/total);
textWidth = (float)font.getStringBounds(s, frc).getWidth();
lm = font.getLineMetrics(s, frc);
sx = (float)(x - textWidth/2);
sy = (float)(y + lm.getAscent()/2);
g2.drawString(s, sx, sy);
theta += phi;

Finally, graphics2d.drawImage(image, 0, 0, this) draw the image of Pie Chart.

Here is the code of PieChartExample.java
import java.awt.*;
import java.awt.event.*;
import java.awt.font.*;
import java.awt.geom.*;
import java.awt.image.*;
import java.text.*;
import javax.swing.*;

public class PieChartExample
{
public static void main(String[] args)
{
JFrame f = new JFrame("Pie Chart");
f.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
f.getContentPane().add(new PieChartPanel());
f.setSize(350,300);
f.setLocation(300,300);
f.setVisible(true);
}
}
class PieChartPanel extends JPanel
{
BufferedImage image;
final int PAD = 30;
Font font;
NumberFormat numberFormat;

public PieChartPanel()
{
font = new Font("Book Antiqua", Font.BOLD, 20);
numberFormat = NumberFormat.getPercentInstance();
addMouseListener(new Visibility(this));
addComponentListener(new ComponentAdapter()
{});
}
protected void paintComponent(Graphics graphics)
{
super.paintComponent(graphics);
Graphics2D graphics2d = (Graphics2D)graphics;
graphics2d.setRenderingHint(RenderingHints.KEY_ANTIALIASING,
RenderingHints.VALUE_ANTIALIAS_ON);
createChartImage();
graphics2d.drawImage(image, 0, 0, this);
}
private void createChartImage()
{
int[] marks = { 98, 76, 90, 85, 75 };
int width = getWidth();
int height = getHeight();
int cp = width/2;
int cq = height/2;
image = new BufferedImage(width, height, BufferedImage.TYPE_INT_RGB);
Graphics2D g2 = image.createGraphics();
g2.setPaint(Color.blue);
g2.fillRect(0, 0, width, height);
g2.setPaint(Color.black);
int pie = Math.min(width,height) - 2*PAD;
g2.draw(new Ellipse2D.Double(cp - pie/2, cq - pie/2, pie, pie));
double total = 0;
for(int j = 0; j < marks.length; j++)
total += marks[j];
double theta = 0, phi = 0;
double p, q;
for(int j = 0; j < marks.length; j++)
{
p = cp + (pie/2) * Math.cos(theta);
q = cq + (pie/2) * Math.sin(theta);
g2.draw(new Line2D.Double(cp, cq, p, q));
phi = (marks[j]/total) * 2 * Math.PI;
p = cp + (9*pie/24) * Math.cos(theta + phi/2);
q = cq + (9*pie/24) * Math.sin(theta + phi/2);
g2.setFont(font);
String st = String.valueOf(marks[j]);
FontRenderContext frc = g2.getFontRenderContext();
float textWidth = (float)font.getStringBounds(st, frc).getWidth();
LineMetrics lm = font.getLineMetrics(st, frc);
float sp = (float)(p - textWidth/2);
float sq = (float)(q + lm.getAscent()/2);
g2.drawString(st, sp, sq);
p = cp + (pie/2 + 4*PAD/5) * Math.cos(theta + phi/2);
q = cq + (pie/2 + 4*PAD/5) * Math.sin(theta+ phi/2);
st = numberFormat.format(marks[j]/total);
textWidth = (float)font.getStringBounds(st, frc).getWidth();
lm = font.getLineMetrics(st, frc);
sp = (float)(p - textWidth/2);
sq = (float)(q + lm.getAscent()/2);
g2.drawString(st, sp, sq);
theta += phi;
}
g2.dispose();
}
public void toggleVisibility()
{
repaint();
}
}
class Visibility extends MouseAdapter
{
PieChartPanel piechart;
public Visibility(PieChartPanel pc)
{
piechart = pc;
}
public void mousePressed(MouseEvent event)
{
if(event.getClickCount() > 1)
piechart.toggleVisibility();
}
}


Output will be displayed as: