Java Graphics - 如何绘制椭圆

import java.awt.Graphics;

import javax.swing.JComponent;
import javax.swing.JFrame;

class MyCanvas extends JComponent {

  public void paint(Graphics g) {
    g.drawOval (10, 10, 200, 200);  
  }
}

public class DrawOval {
  public static void main(String[] a) {
    JFrame window = new JFrame();
    window.setBounds(30, 30, 300, 300);
    window.getContentPane().add(new MyCanvas());
    window.setVisible(true);
  }
}