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);

}
}