Java Graphics_3

package com.han;

import java.awt.Canvas;
import java.awt.Graphics;

import javax.swing.JFrame;

@SuppressWarnings("serial")
public class Graphics_3 extends JFrame {

	private static final int OVAL_WIDTH = 80;
	private static final int OVAL_HEIGHT = 80;

	public Graphics_3() {
		// TODO Auto-generated constructor stub
		Canvas canvas = new Canvas() {
			@Override
			public void paint(Graphics g) {
//				super.paint(g); // for the one containing children components, this is necessary.
				g.drawOval(10, 10, OVAL_WIDTH, OVAL_HEIGHT);
				g.drawOval(80, 10, OVAL_WIDTH, OVAL_HEIGHT);
				g.drawOval(150, 10, OVAL_WIDTH, OVAL_HEIGHT);
				g.drawOval(50, 70, OVAL_WIDTH, OVAL_HEIGHT);
				g.drawOval(120, 70, OVAL_WIDTH, OVAL_HEIGHT);
			}
		};
		this.add(canvas); // add()方法最早出现在Container中，所以我们无法在Canvas中添加组件。 
	}

	/**
	 * @param args
	 */
	public static void main(String[] args) {
		// TODO Auto-generated method stub
		Graphics_3 frame = new Graphics_3();
		frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
		frame.setTitle("Draw circles");
		frame.setSize(300, 200);
		frame.setVisible(true);
	}

}