JAVA-窗口中绘制图形

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


/*
 * 窗口中绘图（长方形，椭圆，对角线，圆）
 * class structure
 * Point2D-Point
 * 							-Ellipse2D
 * Shape-Rectangular Shape |
 * 	  |						-Rectangel2D-Rectangle
 * 	   ---Line2D
 * 
 * 				-Rectangle2D.Float
 * Rectangele2D-|
 * 				-Rectangle2d.Double
 */
public class DrawTest {
	public static void main(String[] args){
		EventQueue.invokeLater(new Runnable()
		{
			public void run()
			{
				DrawFrame frame = new DrawFrame();
				frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
				frame.setVisible(true);
			}
		});
	}
}
/**
 * A frame that contains apanel with drawings
 */
class DrawFrame extends JFrame
{
	public DrawFrame()
	{
		setTitle("DrawFrame");
		setSize(DEFAULT_WIDTH,DEFAULT_HEIGHT);
		//add a panel to frame
		DrawComponent component = new DrawComponent();
		add(component);
	}
	public static final int DEFAULT_WIDTH = 400;
	public static final int DEFAULT_HEIGHT = 400;
}
/**
 * A component that displays rectangles and ellipses
 */
class DrawComponent extends JComponent
{
	public void paintComponent(Graphics g)
	{
		Graphics2D g2 = (Graphics2D)g;
		//draw a rectangle
		double leftX = 100;
		double topY = 100;
		double width = 200;
		double height = 150;
		
		Rectangle2D  rect = new Rectangle2D.Double(leftX,topY,width,height);
		g2.draw(rect);
		
		//draw a ellipse
		//*Ellipse2D ellipse = new Ellipse2D.Double(leftX,topY,width,height);
		Ellipse2D ellipse = new Ellipse2D.Double();
		ellipse.setFrame(rect);
		g2.draw(ellipse);
		
		//draw a diagonal line
		g2.draw(new Line2D.Double(leftX,topY,leftX+width,topY+height));
		
		//draw a circle with the same center
		double centerX = leftX + width/2;
		double centerY = topY + height/2;
		double radius = 150;
		Ellipse2D circle = new Ellipse2D.Double();
		circle.setFrameFromCenter(centerX, centerY,centerX+radius,centerY+radius);
		//*Ellipse2D circle = new Ellipse2D.Double(leftX,topY,radius*2,radius*2);		
		g2.draw(circle);
		
	}
}