starondot.java

Java程序设计(美) David D. Riley著 机械工业出版社 书籍配套 代码

import javax.swing.*;
import java.awt.*;

/** StarOnDotSupplier Class 
 * Author: David D. Riley
 * Date: April, 2004
 *
 * Class Invariant
 *  This class draws a filled circle in the background color
 *  with a 5-pointed star inscribed within the circle and
 *  using the foreground color.  This minimum of getWidth()
 *  and getHeight() is used for the dot's diameter.
 */
public class StarOnDot extends JComponent  {

	public StarOnDot()  {
        super();
	}

    public void paint(Graphics g)  {
        double diameter = getWidth();
        if (getHeight() < diameter)
            diameter = getHeight();
            
        // draw the filled circle
        g.setColor( getBackground() );
        g.fillOval(0, 0, (int)diameter-1, (int)diameter-1);
        
        /*  Draw the 5-pointed star using points at the following degree
         *  measurements (270 degrees would be the top apex of the star):
         *          54, 126, 198, 270, and 342  degrees  */
        g.setColor( getForeground() );
        g.drawLine( (int)(diameter/2+Math.cos(Math.toRadians(54))*diameter/2),
                    (int)(diameter/2+Math.sin(Math.toRadians(54))*diameter/2),
                    (int)(diameter/2+Math.cos(Math.toRadians(198))*diameter/2),
                    (int)(diameter/2+Math.sin(Math.toRadians(198))*diameter/2) );
        g.drawLine( (int)(diameter/2+Math.cos(Math.toRadians(126))*diameter/2),
                    (int)(diameter/2+Math.sin(Math.toRadians(126))*diameter/2),
                    (int)(diameter/2+Math.cos(Math.toRadians(270))*diameter/2),
                    (int)(diameter/2+Math.sin(Math.toRadians(270))*diameter/2) );
        g.drawLine( (int)(diameter/2+Math.cos(Math.toRadians(198))*diameter/2),
                    (int)(diameter/2+Math.sin(Math.toRadians(198))*diameter/2),
                    (int)(diameter/2+Math.cos(Math.toRadians(342))*diameter/2),
                    (int)(diameter/2+Math.sin(Math.toRadians(342))*diameter/2) );
        g.drawLine( (int)(diameter/2+Math.cos(Math.toRadians(270))*diameter/2),
                    (int)(diameter/2+Math.sin(Math.toRadians(270))*diameter/2),
                    (int)(diameter/2+Math.cos(Math.toRadians(54))*diameter/2),
                    (int)(diameter/2+Math.sin(Math.toRadians(54))*diameter/2) );
        g.drawLine( (int)(diameter/2+Math.cos(Math.toRadians(342))*diameter/2),
                    (int)(diameter/2+Math.sin(Math.toRadians(342))*diameter/2),
                    (int)(diameter/2+Math.cos(Math.toRadians(126))*diameter/2),
                    (int)(diameter/2+Math.sin(Math.toRadians(126))*diameter/2) );

        paintChildren(g);
   }
}