New to Java

I've seen this code many times, but I cannot get it to work:

MediaTracker tracker;

tracker = new MediaTracker(this);

Image image = Toolkit.getDefaultToolkit().getImage("test.gif");
tracker.addImage(image, 0);

try{
            tracker.waitForID(0);
        } catch (Exception ex) {
            System.out.println(ex.getMessage());
        }

but this works:

MediaTracker tracker;

tracker = new MediaTracker(this);

Image image = Toolkit.getDefaultToolkit().getImage("C:/path to image/test.gif");
tracker.addImage(image, 0);

try{
            tracker.waitForID(0);
        } catch (Exception ex) {
            System.out.println(ex.getMessage());
        }

Why doesn't it load the gif when just a filename is present? I've got the image in the same directory as the .java file and as the .class file.

Thanks for any help,
Ryan