Chapter 32 Exercise 2, Introduction to Java Programming, Tenth Edition Y. Daniel LiangY.

32.2 (Visualize data) Write a program that displays the number of students in each department in a pie chart and a bar chart, as shown in Figure 32.27b. The number of students for each department can be obtained from the Student table (see Figure 32.4) using the following SQL statement:
select deptId, count(*)
from Student
where deptId is not null
group by deptId;

import javax.swing.*;
import javax.swing.border.EmptyBorder;

import java.sql.*;
import java.util.ArrayList;
import java.awt.*;

public class Exercise02 extends JApplet {
 private static final long serialVersionUID = 1L;
 private ArrayList<Students> list = new ArrayList<>();
 
 public void init() {
  initializeDB();
  JPanel jPanel1 = new JPanel(new GridLayout(1, 2, 5, 5));
  jPanel1.setBorder(new EmptyBorder(5, 5, 5, 5));
  jPanel1.add(new DrawPieChart());
  jPanel1.add(new DrawBarChart());
  setLayout(new BorderLayout());
  add(jPanel1);

 }

 private void initializeDB() {
  try {
   Class.forName("com.mysql.jdbc.Driver");
   Connection connection = DriverManager.getConnection("jdbc:mysql://localhost/javabook", "root", "root");
   Statement statement = connection.createStatement();
   ResultSet rset = statement.executeQuery("select deptId, count(*) from Student where deptId is not null group by deptId;");
   while(rset.next()) {
    list.add(new Students(rset.getString(1), Integer.parseInt(rset.getString(2))));
   }
   System.out.println(list);
  } catch (Exception ex) {
   ex.printStackTrace();
  }
 }
 
 class DrawPieChart extends JPanel {
  private static final long serialVersionUID = 1L;

  @Override
  public Dimension getPreferredSize() {
   return new Dimension(300, 300);
  }
  
  @Override
  protected void paintComponent(Graphics g) {
   super.paintComponent(g);
   int width = getWidth();
   int height = getHeight();
   int minLen = (width < height ? width : height);
   int startAngle = 0;
   double sum = 0;
   for (int i = 0; i < list.size(); i++) {
    sum += list.get(i).getCount();
   }
   
   for (int i = 0; i < list.size(); i++) {
    
    System.out.println(startAngle);
    g.setColor(list.get(i).getColor());
    g.fillArc((width - minLen) / 2 + 10, (height - minLen) / 2 + 10, minLen - 20, minLen - 20, startAngle, (int)Math.ceil((360 / sum) * list.get(i).getCount()));
    double textAngle = Math.toRadians(360 - (startAngle + startAngle + (int)Math.ceil((360 / sum) * list.get(i).getCount())) / 2);
    startAngle = startAngle + (int)Math.ceil((360 / sum) * list.get(i).getCount());
    g.setColor(Color.BLACK);

    int x2 = (int)((width / 2) + Math.cos(textAngle) * (minLen / 2 - 15));
    int y2 = (int)((height / 2) + Math.sin(textAngle) * (minLen / 2 - 15));      
    g.drawString(list.get(i).getName(), x2, y2);
    
   }
   
   
  }

 }
 
 class DrawBarChart extends JPanel {

  private static final long serialVersionUID = 1L;

  @Override
  public Dimension getPreferredSize() {
   return new Dimension(300, 300);
  }
  @Override
  protected void paintComponent(Graphics g) {
   super.paintComponent(g);
   int width = getWidth();
   int height = getHeight();
   int step = width / list.size();
   int widthStep = step - 10;
   int heightStep = list.get(0).getCount();
   for (int i = 1; i < list.size(); i++) {
    if(list.get(i).getCount() > heightStep) {
     heightStep = list.get(i).getCount();
    }
   }
   heightStep = (int)((height - 20.0) / heightStep);
   for (int i = 0; i < list.size(); i++) {
    g.setColor(list.get(i).getColor());
    g.fillRect(5 + step * i, height - (heightStep * list.get(i).getCount()) - 5, widthStep, (heightStep * list.get(i).getCount()) - 5);
    g.setColor(Color.BLACK);
    g.drawString(list.get(i).getName(), 5 + step * i, height - (heightStep * list.get(i).getCount()) - 10);
   }
   g.drawLine(0, height - 10, getWidth(), height - 10);
  }

 }

 class Students {
  private String name;
  private int count;
  private Color color;
  
  public Students(String name, int count) {
   this.name = name;
   this.count = count;
   this.color = new Color((int)(Math.random() * 256), (int)(Math.random() * 256), (int)(Math.random() * 256));
  }

  public String getName() {
   return name;
  }

  public void setName(String name) {
   this.name = name;
  }

  public int getCount() {
   return count;
  }

  public void setCount(int count) {
   this.count = count;
  }
  
  public Color getColor() {
   return color;
  }

  public void setColor(Color color) {
   this.color = color;
  }

  @Override
  public String toString() {
   return name + ":" + count;
  }
  
 }
 
 /** Main method */
 public static void main(String[] args) {
  Exercise02 applet = new Exercise02();
  JFrame frame = new JFrame();
  frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
  frame.setTitle("Exercise02");
  frame.getContentPane().add(applet, BorderLayout.CENTER);
  applet.init();
  applet.start();
  frame.pack();
  frame.setLocationRelativeTo(null);
  frame.setVisible(true);
 }
}