java使用swing编写界面不出现，应该怎么解决，急急急！！！！！！！！！

Image getImage(String filename) {
URLClassLoader urlLoader = (URLClassLoader)this.getClass().getClassLoader();
String url = null;
Image image = null;
url = urlLoader.findResource(filename);
image = Toolkit.getDefaultToolkit().getImage(url);
MediaTracker mediaTracker = new MediaTracker(this);
try {

    mediaTracker.addImage(image, 0);
    mediaTracker.waitForID(0);
} 
catch (InterruptedException_ex) {
    image = null;
    // TODO: handle exception
}
if (mediaTracker.isErrorID(0)) {
    image = null;
}
return image;

}