JFrame的图标无法显示

Question

I've got a Java application with Swing's JFrame as a main GUI unit. I've set the icon to it via setIconImage(). When I run this program in NetBeans, everything works fine and the frame's icon displays. But when I compile it and try to run jar-file (with JRE7), the application has standard icon with Duke. How do I change that icon when running app outside NetBeans?

UPD: OK, here's the code:

public static void main(String[] args) throws IOException{
    URL imgUrl = Polygon.class.getResource("/imgs/icon.png");
    Image img = ImageIO.read(imgUrl);

    JFrame f = new JFrame();
    f.setSize(new Dimension(500, 500));
    f.setIconImage(img);
    f.setVisible(true);
}

UPD2: I've added this line to the end of the code:

    JOptionPane.showMessageDialog(null, new ImageIcon(img));

Everything's fine with the image! It loads! BUT it's not displayed as the icon.

Answer 1

When you run the application from inside Netbeans, the files from your project folder are available, but if you run the compiled JAR yourself they may not.

Read this example (note the comments) to load your image properly.

Answer 2

Try getClass().getResource("imgs/icon.png") . It works for me. Note the difference between absolute and relative path. You may not need the leading / .