图片读取显示失败？求解？解决方法

package c2;//JSplashWindow.java//Demos how to show a splash windowimport javax.swing.*;import java.awt.*;import java.net.*;public class JSplashWindow extends JWindow implements Runnable {    Thread splashThread = null;    public JSplashWindow() {        setCursor(Cursor.getPredefinedCursor(Cursor.WAIT_CURSOR));        JPanel splash = new JPanel(new BorderLayout());        URL url = getClass().getResource("images/winter.jpg");//错误在这变成/images/winter.jpg也不对//我想执行这句        if (url != null) {            splash.add(new JLabel(new ImageIcon(url)), BorderLayout.CENTER);        }//这句是测试url有没有被赋值的  被执行了。。。        if(url==null)        {            splash.add(new JLabel("helloworld"));        }                setContentPane(splash);        Dimension screen = getToolkit().getScreenSize();        pack();        setLocation((screen.width - getSize().width) / 2,                (screen.height - getSize().height) / 2);    }    public void start() {        this.toFront();        splashThread = new Thread(this);        splashThread.start();    }    public void run() {        try {            show();            Thread.sleep(5000);        } catch (Exception ex) {            ex.printStackTrace();        }        this.dispose();    }    static void showFrame(String title) {        JFrame frame = new JFrame(title);        frame.setSize(400, 300);        frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);        // Center the window        Dimension screenSize = Toolkit.getDefaultToolkit().getScreenSize();        Dimension frameSize = frame.getSize();        if (frameSize.height > screenSize.height) {            frameSize.height = screenSize.height;        }        if (frameSize.width > screenSize.width) {            frameSize.width = screenSize.width;        }        frame.setLocation((screenSize.width - frameSize.width) / 2,                (screenSize.height - frameSize.height) / 2);        frame.setVisible(true);    }    public static void main(String[] args) {        showFrame("Demo splash window");        JSplashWindow splash = new JSplashWindow();        splash.start();    }}