The Quintessential Drawing Program
This example creates a frame and draws an oval within the frame. 

 import java.awt.*;
 import javax.swing.*;
     
 class BasicDraw extends JComponent {
   public void paint(Graphics g) {
     Graphics2D g2d = (Graphics2D)g;
     
     g2d.drawOval(0, 0, getSize().width-1, 
       getSize().height-1);
   }
     
   public static void main(String[] args) {
     JFrame frame = new JFrame();
     frame.getContentPane().add(new BasicDraw());
     int frameWidth = 300;
     int frameHeight = 300;
     frame.setSize(frameWidth, frameHeight);
     frame.setVisible(true);
   }
 }