图片无法显示——————image文件夹放置正确

[码了个农]

import javax.swing.*;

public class TestButtonIcons extends JFrame{

    /**
     * @param args
     */
    public static void main(String[] args){
        JFrame frame = new TestButtonIcons();
        frame.setTitle ("ButtonICons");
        frame.setSize(500,200);
        frame.setLocationRelativeTo(null);
        frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
        frame.setVisible (true);
    }
    
    public TestButtonIcons(){
        ImageIcon usIcon = new ImageIcon("image/usIcon.gif");
        ImageIcon caIcon = new ImageIcon("image/caIcon.gif");
        ImageIcon ukIcon = new ImageIcon("image/ukIcon.gif");
        
        JButton jbt = new JButton("Click it",usIcon);
        jbt.setPressedIcon(caIcon);
        jbt.setRolloverIcon(ukIcon);
        
        add(jbt);
    }
}

图片放到了 D:\work\TestSwing\image