/** Returns an ImageIcon, or null if the path was invalid. */
protected ImageIcon createImageIcon(String path,
String description) {
java.net.URL imgURL = getClass().getResource(path);
if (imgURL != null) {
return new ImageIcon(imgURL, description);
} else {
System.err.println("Couldn't find file: " + path);
return null;
}
}


Example for Loading Images in Frame

public class IconDemoApp extends JFrame {

private JLabel photographLabel = new JLabel();
private JToolBar buttonBar = new JToolBar();

private String imagedir = "images/";

private MissingIcon placeholderIcon = new MissingIcon();

/**
* List of all the descriptions of the image files. These correspond one
to
* one with the image file names
*/
private String[] imageCaptions = { "Original SUNW Logo", "The
Clocktower",
"Clocktower from the West", "The Mansion", "Sun Auditorium"};

/**
* List of all the image files to load.
*/
private String[] imageFileNames = { "sunw01.jpg", "sunw02.jpg",
"sunw03.jpg", "sunw04.jpg", "sunw05.jpg"};

/**
* Main entry point to the demo. Loads the Swing elements on the "Event
* Dispatch Thread".
*
* @param args
*/
public static void main(String args[]) {
SwingUtilities.invokeLater(new Runnable() {
public void run() {
IconDemoApp app = new IconDemoApp();
app.setVisible(true);
}
});
}

/**
* Default constructor for the demo.
*/
public IconDemoApp() {
setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
setTitle("Icon Demo: Please Select an Image");

// A label for displaying the pictures
photographLabel.setVerticalTextPosition(JLabel.BOTTOM);
photographLabel.setHorizontalTextPosition(JLabel.CENTER);
photographLabel.setHorizontalAlignment(JLabel.CENTER);
photographLabel.setBorder(BorderFactory.createEmptyBorder(5, 5, 5,
5));

// We add two glue components. Later in process() we will add
thumbnail buttons
// to the toolbar inbetween thease glue compoents. This will center
the
// buttons in the toolbar.
buttonBar.add(Box.createGlue());
buttonBar.add(Box.createGlue());

add(buttonBar, BorderLayout.SOUTH);
add(photographLabel, BorderLayout.CENTER);

setSize(400, 300);

// this centers the frame on the screen
setLocationRelativeTo(null);

// start the image loading SwingWorker in a background thread
loadimages.execute();
}

/**
* SwingWorker class that loads the images a background thread and calls
publish
* when a new one is ready to be displayed.
*
* We use Void as the first SwingWroker param as we do not need to
return
* anything from doInBackground().
*/
private SwingWorker loadimages = new
SwingWorker() {

/**
* Creates full size and thumbnail versions of the target image
files.
*/
@Override
protected Void doInBackground() throws Exception {
for (int i = 0; i < imageCaptions.length; i++) {
ImageIcon icon;
icon = createImageIcon(imagedir + imageFileNames[i],
imageCaptions[i]);

ThumbnailAction thumbAction;
if(icon != null){

ImageIcon thumbnailIcon = new
ImageIcon(getScaledImage(icon.getImage(), 32, 32));

thumbAction = new ThumbnailAction(icon, thumbnailIcon,
imageCaptions[i]);

}else{
// the image failed to load for some reason
// so load a placeholder instead
thumbAction = new ThumbnailAction(placeholderIcon,
placeholderIcon, imageCaptions[i]);
}
publish(thumbAction);
}
// unfortunately we must return something, and only null is
valid to
// return when the return type is void.
return null;
}

/**
* Process all loaded images.
*/
@Override
protected void process(List chunks) {
for (ThumbnailAction thumbAction : chunks) {
JButton thumbButton = new JButton(thumbAction);
// add the new button BEFORE the last glue
// this centers the buttons in the toolbar
buttonBar.add(thumbButton, buttonBar.getComponentCount() -
1);
}
}
};

/**
* Creates an ImageIcon if the path is valid.
* @param String - resource path
* @param String - description of the file
*/
protected ImageIcon createImageIcon(String path,
String description) {
java.net.URL imgURL = getClass().getResource(path);
if (imgURL != null) {
return new ImageIcon(imgURL, description);
} else {
System.err.println("Couldn't find file: " + path);
return null;
}
}

/**
* Resizes an image using a Graphics2D object backed by a BufferedImage.
* @param srcImg - source image to scale
* @param w - desired width
* @param h - desired height
* @return - the new resized image
*/
private Image getScaledImage(Image srcImg, int w, int h){
BufferedImage resizedImg = new BufferedImage(w, h,
BufferedImage.TYPE_INT_RGB);
Graphics2D g2 = resizedImg.createGraphics();
g2.setRenderingHint(RenderingHints.KEY_INTERPOLATION,
RenderingHints.VALUE_INTERPOLATION_BILINEAR);
g2.drawImage(srcImg, 0, 0, w, h, null);
g2.dispose();
return resizedImg;
}

/**
* Action class that shows the image specified in it's constructor.
*/
private class ThumbnailAction extends AbstractAction{

/**
*The icon if the full image we want to display.
*/
private Icon displayPhoto;

/**
* @param Icon - The full size photo to show in the button.
* @param Icon - The thumbnail to show in the button.
* @param String - The descriptioon of the icon.
*/
public ThumbnailAction(Icon photo, Icon thumb, String desc){
displayPhoto = photo;

// The short description becomes the tooltip of a button.
putValue(SHORT_DESCRIPTION, desc);

// The LARGE_ICON_KEY is the key for setting the
// icon when an Action is applied to a button.
putValue(LARGE_ICON_KEY, thumb);
}

/**
* Shows the full image in the main area and sets the application
title.
*/
public void actionPerformed(ActionEvent e) {
photographLabel.setIcon(displayPhoto);
setTitle("Icon Demo: " +
getValue(SHORT_DESCRIPTION).toString());
}
}
}