帮忙看下实现菱形按钮的代码错误？
import   java.awt.Color;
import   java.awt.FlowLayout;
import   java.awt.Graphics;
import   java.awt.Image;
import   java.awt.Toolkit;
import   java.awt.event.ActionEvent;
import   java.awt.event.ActionListener;

import   javax.swing.Icon;
import   javax.swing.ImageIcon;
import   javax.swing.JButton;
import   javax.swing.JFrame;
import   javax.swing.JOptionPane;

public   class   TestButton   extends   JButton   {
JFrame   f;

JButton0   b0;

Image   img;

JButton   b;

ImageIcon   ii;

public   TestButton()   {
init();
}

public   void   init()   {

img   =   Toolkit.getDefaultToolkit().getImage(
TestButton.class.getResource( "1.jpg "));
ii   =   new   ImageIcon(img);
f   =   new   JFrame( "test ");
b0   =   new   JButton0( "OK ",   img);

f.add(b0);
b0.setBounds(100,   100,   100,   100);
b0.addActionListener(new   ActionListener()   {

public   void   actionPerformed(ActionEvent   arg0)   {
JOptionPane.showMessageDialog(f,   "hehe！ ");
}

});
f.setLayout(new   FlowLayout());
f.setSize(400,   400);
f.setVisible(true);

}

public   static   void   main(String   args[])   {
new   TestButton();
}

}

class   JButton0   extends   JButton   {

Image   img;

String   text;

public   JButton0()   {
this.setSize(100,   100);
}

public   JButton0(Image   img)   {
this.img   =   img;
}

public   JButton0(Icon   icon)   {
this.setIcon(icon);
}

public   JButton0(String   text)   {
this.text   =   text;
}

public   JButton0(String   text,   Image   img)   {
this.text   =   text;
this.img   =   img;
}

public   void   paint(Graphics   g)   {
int[]   x   =   {   0,   50,   100,   50   };
int[]   y   =   {   50,   0,   50,   100   };
g.drawPolygon(x,   y,   4);
g.setColor(Color.blue);
g.fillPolygon(x,   y,   4);
if   (img   !=   null)   {
g.drawImage(img,   25,   25,   this.getHeight()   /   2,   this.getWidth()   /   2,
this);
}
g.setColor(Color.RED);
g.drawString(text,   43,   55);
}
}
在eclipse
运行错误提示
Uncaught   error   fetching   image:
java.lang.NullPointerException
at   sun.awt.image.URLImageSource.getConnection(URLImageSource.java:97)
at   sun.awt.image.URLImageSource.getDecoder(URLImageSource.java:106)
at   sun.awt.image.InputStreamImageSource.doFetch(InputStreamImageSource.java:240)
at   sun.awt.image.ImageFetcher.fetchloop(ImageFetcher.java:172)
at   sun.awt.image.ImageFetcher.run(ImageFetcher.java:136)

高手们帮忙改下？？谢谢各位？

------解决方案--------------------
img = Toolkit.getDefaultToolkit().getImage(