JPanal上加图片的问题！

import java.awt.BorderLayout;

import java.awt.Dimension;

import javax.swing.JFrame;

import javax.swing.JPanel;

import javax.swing.*;

import java.awt.*;

public class Frame1 extends JFrame {

JPanel contentPane;

JLabel jLabel1 = new JLabel();

BorderLayout borderLayout1 = new BorderLayout();

BG background = new BG();

public Frame1() {

try {

setDefaultCloseOperation(EXIT_ON_CLOSE);

jbInit();

} catch (Exception exception) {

exception.printStackTrace();

}

}

/**

* Component initialization.

*

* @throws java.lang.Exception

*/

private void jbInit() throws Exception {

contentPane = (JPanel) getContentPane();

contentPane.setLayout(borderLayout1);

setSize(new Dimension(400, 300));

setTitle("Frame Title");

jLabel1.setText("jLabel1");

contentPane.add(background, java.awt.BorderLayout.SOUTH); }

class BG extends JPanel {

public void paintComponent(Graphics g) {

super.paintComponent(g);

Image img=Toolkit.getDefaultToolkit().getImage("F:\\1.jpg");

g.drawImage(img,0,0,this.getSize().width,this.getSize().height,this);//是怎么产生的？？？？？？

}

}//我是想在jPanal上加图片！ }