利用toolkit改变java小图标

import javax.swing.*;
import javax.swing.ImageIcon;
import java.awt.Toolkit;

public class Iconexample extends JFrame
{
ImageIcon ii[]=new ImageIcon[12];
JButton jb;
JPanel jp;
public Iconexample()
{
super("IVON");
this.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
jp=new JPanel(null);
ii[0]=new ImageIcon("1.png");
jb=new JButton(ii[0]);
jb.setBounds(0,0,ii[0].getIconWidth(),ii[0].getIconHeight());
jp.add(jb);
add(jp);
setSize(ii[0].getIconWidth(),ii[0].getIconHeight());
setIconImage(Toolkit.getDefaultToolkit().getImage("2.png"));
setVisible(true);
}
public static void main (String[] args)
{
Iconexample aaassc=new Iconexample();
}

}