swings

Hi,

     I am working on swings as a desktop application.
How to implement jpanel on background images of a JFrame?

I am not able to get the panel if i got the image and
i am not able to get image if I got the panel.

import javax.swing.*;
import java.awt.*;
import java.awt.Image;

public class PaneExample extends JFrame {
  static Image img,_image;
  public PaneExample() {
    super("Login");

    setDefaultCloseOperation(EXIT_ON_CLOSE);

    JPanel opaque = createNested(true);
    Image img=Toolkit.getDefaultToolkit().getImage("g.gif");;
        getContentPane().setLayout(new
FlowLayout(FlowLayout.CENTER,300,400));
    getContentPane().add(opaque);

  }
        public void paint(Graphics g) {

                        if(img!= null) {
                        int x = 0, y = 0;
                        while(y < img.getHeight(null)) {
                                x = 0;
                                while(x< getSize().width) {
                                        g.drawImage(img, x, y, this);
                                x= x + img.getWidth(null);
                                }
                                y = y + img.getHeight(null);
                        }
                        g.setFont(new Font("Helvetica", Font.PLAIN,
40));

                g.drawImage(img,10,10,this);

                  }else {
                        g.clearRect(0, 0, getSize().width,
getSize().height);

}

public static void main(String[] args) {
    PaneExample oe = new PaneExample();

        Graphics2D01 guiObj = new Graphics2D01();
        int wid=guiObj.getWidth();
        int height=guiObj.getHeight();
         System.out.println(wid + "" + height);
    oe.setSize(wid,height);

    oe.setVisible(true);
  }

  public JPanel createNested(boolean opaque) {
    JPanel outer = new JPanel(new FlowLayout());
        JLabel l1 = new JLabel("User Name");
        outer.add(l1);
        JTextField tf1= new JTextField(10);
    outer.add(tf1);
        JLabel l2 = new JLabel("password");
        outer.add(l2);
        JTextField tf2= new JTextField(10);
    outer.add(tf2);
        JButton b1 = new JButton("Login");
        outer.add(b1);
outer.setPreferredSize(new Dimension(200, 100));

    outer.setBackground(Color.blue);

    return outer;
  }