一个简单的绘制饼图的 Java Bean 实例详解编程语言

import java.awt.*; 
 
/** 
 * Simple charting bean. This version just draws a Pie Chart. 
 * 
 * It doesn't even label the pie slices; that is left as a 
 * (non-trivial) exercise for the reader. Please read the 
 * Technical Report "How Hard can it be to draw Pie Charts?" by Chris 
 * van Wyck, Purdue/Bell Labs, 1989??, before you decide how easy 
 * the work is going to be! 
 */ 
public class ChartBean extends Component { 
 
   /** The title to print on the chart */ 
   protected String title; 
 
   /** the data to draw */ 
   protected ChartData data[]; 
 
   /** degrees in a circle */ 
   public static final int CIRCLE = 360; 
 
   /** a set of colors to draw the pies in */ 
   protected Color[] colors = { 
      Color.red, 
      Color.blue, 
      Color.green, 
      Color.pink, 
      Color.orange 
   }; 
 
   /** Construct a ChartBean with a title */ 
   public ChartBean(String s) { 
      title = s; 
      setBackground(Color.white); 
   } 
   /** Construct a ChartBean with no title (no-arg constructor 
    * required for Beans). 
    */ 
   public ChartBean() { 
       this(null); 
   } 
 
   public void setLabel(String s) { 
      title = s; 
   } 
 
   public String getLabel() { 
      return title; 
   } 
   public void setData(ChartData[] newStuff) { 
      data = newStuff; 
      repaint(); 
   } 
 
   public void paint(Graphics g) { 
      Dimension sz = getSize(); 
      int w = sz.width, h = sz.width; 
 
      if (title != null) 
         g.drawString(title, w/10, (int)(h*.9)); 
 
      if (data == null || data.length == 0) { 
         g.drawOval(0, 0, w, h); 
         g.drawString("Please provide some data!", w/10, h/2); 
         return; 
      } 
 
      int total = 0; 
      int angle = 0; 
      int rad = 0;   // "radians" (actually degrees) to draw 
      int colNum = 0; 
 
      for (int i=0; i<data.length; i++) 
         total += data[i].value; 
      for (int i=0; i<data.length; i++) { 
         rad = (int)(CIRCLE * ((float)data[i].value / (float)total)); 
         // System.out.println("data: "+data[i].name+";"+data[i].value+ 
         //   ",rad="+rad); 
         g.setColor(colors[colNum++]); 
         colNum%=colors.length;   // keep it in bounds 
         g.fillArc(0, 0, w, h, angle, rad); 
         angle += rad; 
      } 
   } 
 
   public Dimension getMinimumSize() { 
      return new Dimension(100, 120); 
   } 
   public Dimension getPreferredSize() { 
      return new Dimension(200, 240); 
   } 
}