Java Graphics - 如何绘制饼图

import java.awt.Color;
import java.awt.Graphics;
import java.awt.Graphics2D;
import java.awt.Rectangle;

import javax.swing.JComponent;
import javax.swing.JFrame;

class Slice {
  double value;
  Color color;

  public Slice(double value, Color color) {
    this.value = value;
    this.color = color;
  }
}

class MyComponent extends JComponent {
  Slice[] slices = { new Slice(5, Color.black), new Slice(33, Color.green),
      new Slice(20, Color.yellow), new Slice(15, Color.red) };

  MyComponent() {

  }
  public void paint(Graphics g) {
    drawPie((Graphics2D) g, getBounds(), slices);
  }

  void drawPie(Graphics2D g, Rectangle area, Slice[] slices) {
    double total = 0.0D;
    for (int i = 0; i < slices.length; i++) {
      total += slices[i].value;
    }

    double curValue = 0.0D;
    int startAngle = 0;
    for (int i = 0; i < slices.length; i++) {
      startAngle = (int) (curValue * 360 / total);
      int arcAngle = (int) (slices[i].value * 360 / total);

      g.setColor(slices[i].color);
      g.fillArc(area.x, area.y, area.width, area.height, startAngle, arcAngle);
      curValue += slices[i].value;
    }
  }
}

public class PieChart {
  public static void main(String[] argv) {
    JFrame frame = new JFrame();
    frame.getContentPane().add(new MyComponent());
    frame.setSize(300, 200);
    frame.setVisible(true);

  }
}