Big Java 上的一个java 2D的例子，个人认为结构很好。

package app3;

import java.awt.Color;
import java.awt.Graphics;
import java.awt.Graphics2D;
import java.awt.Rectangle;
import java.awt.geom.Ellipse2D;
import java.awt.geom.Line2D;
import javax.swing.JPanel;
import javax.swing.JComponent;
/**
   A component that draws an alien face.
*/
public class FaceComponent extends JComponent
{
   public void paintComponent(Graphics g)
   {
      // Recover Graphics2D
      Graphics2D g2 = (Graphics2D) g;
      // Draw the head
      Ellipse2D.Double head = new Ellipse2D.Double(5, 10, 100, 150);
      g2.draw(head);
      // Draw the eyes
      Line2D.Double eye1 = new Line2D.Double(25, 70, 45, 90);
      g2.draw(eye1);
      Line2D.Double eye2 = new Line2D.Double(85, 70, 65, 90);
      g2.draw(eye2);
      // Draw the mouth
      Rectangle mouth = new Rectangle(30, 130, 50, 5);
      g2.setColor(Color.RED);
      g2.fill(mouth);
      // Draw the greeting
      g2.setColor(Color.BLUE);  
      g2.drawString("Hello, World!", 5, 175);
   }
}

 

 

package app3;

import javax.swing.JFrame;
public class FaceViewer
{
   public static void main(String[] args)
   {
      JFrame frame = new JFrame();
      frame.setSize(300, 400);
      frame.setTitle("An Alien Face");
      frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
 
      FaceComponent component = new FaceComponent();
      frame.add(component);
      frame.setVisible(true);
   }
}