chooser=new JFileChooser();
chooser.setFileView(new FileIconView(filter, new ImageIcon()));

class ImagePreviewer extends JLabel{
    public ImagePreviewer(JFileChooser chooser){
       setPreferredSize(new Dimension(100,100));
       setBorder(BorderFactory.createEtchedBorder());
       chooser.addPropertyChangeListener(new PropertyChangeListener() {
        public void propertyChange(PropertyChangeEvent event) {
            if(event.getPropertyName()==JFileChooser.SELECTED_FILE_CHANGED_PROPERTY){
                File f=(File) event.getNewValue();
                if(f==null){
                   setIcon(null);
                    return;
                   }
                ImageIcon icon=new ImageIcon(f.getName());
                int imgWidth=icon.getIconWidth();//获得图片宽度
                int imgHeight=icon.getIconHeight();//获得图片高度
                int conWidth=getWidth();//得到组件宽度
                int conHeight=getHeight();//得到组件高度
                int reImgWidth;//保存图片更改宽度后的值
                int reImgHeight;//保存图片更改高度后的值
                if(imgWidth/imgHeight>=conWidth/conHeight){
                    if(imgWidth>conWidth){
                        reImgWidth=conWidth;
                        reImgHeight=imgHeight*reImgWidth/imgWidth;
                    }else{
                        reImgWidth=imgWidth;
                        reImgHeight=imgHeight;
                    }
                }else{
                    if(imgWidth>conWidth){
                        reImgHeight=conHeight;
                        reImgWidth=imgWidth*reImgHeight/imgHeight;
                    }else{
                        reImgWidth=imgWidth;
                        reImgHeight=imgHeight;
                    }
                }
                icon=new ImageIcon(icon.getImage().getScaledInstance            (reImgWidth,reImgHeight, Image.SCALE_DEFAULT));
                    setIcon(icon);
                    
                    
                }
            }
        });
    }
}