triangle.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 8.17)

import java.awt.Graphics;
import javax.swing.JComponent;
public class Triangle extends JComponent {

	/**		post:	getbackGround() is an invisible color
	 *				and  getWidth() == getHeight() == 0 
	 */  
	public Triangle( )   {
		super( );
	}
	
	/**	post:	a Triangle is drawn with vertices at (getWidth()/2, 0),
	 *					(0, getHeight()-1) and (getWidth()-1, getHeight()-1)
	 *			and  the color of thhe triangle is getBackground() 
	 */
	public  void  paint( Graphics g )   {
		g.setColor( getBackground() );
		g.drawLine( getWidth()/2, 0, 0, getHeight()-1 );
		g.drawLine( 0, getHeight()-1, getWidth()-1, getHeight()-1 );
		g.drawLine( getWidth()/2, 0, getWidth()-1, getHeight()-1 );
	}
}