cube.java

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

// (Figure 8.21)
import java.awt.Graphics;
import javax.swing.JComponent;
public class Cube extends JComponent {

	/**		post:	getbackGround() is an invisible color
	 *				and  getX() == x  and  getY() == y
	 *				and  getWidth() == getHeight() == s 
	 */  
	public Cube(int x, int y, int s)   {
		super( );
   		setBounds(x, y, s, s);
        
	}
	
	/**		pre:	getWidth() == getHeight()
	 *  	post:	a cube is drawn with vertices at (getWidth()/2, 0),
	 *					(0, getHeight()-1) and (getWidth()-1, getHeight()-1)
	 *				and  the color of the triangle is getBackground() 
	 */
	public  void  paint( Graphics g )   {
		int s = getWidth()-1;
		g.setColor( getBackground() );
		g.drawRect(0, s/4, s*3/4, s*3/4);
		g.drawLine(0, s/4, s/4, 0);     //left diagonal line
		g.drawLine(s*3/4, s/4, s, 0);   //right top diagonal line
		g.drawLine(s/4, 0, s, 0);       //top horizontal line
		g.drawLine(s*3/4, s, s, s*3/4); //right bottom diagonal line
		g.drawLine(s, 0, s, s*3/4);     //back vertical line
		g.setColor( getForeground() );
		g.fillOval(s/4, s/2, s/4, s/4);
	}
}