public URL getURL()
    {
        if( url == null )
        {
            // Check if the file is online or inside the JAR:
            if( filename.matches( SoundSystemConfig.PREFIX_URL ) )
            {
                // Online
                try
                {
                    url = new URL( filename );
                }
                catch( Exception e )
                {
                    errorMessage( "Unable to access online URL in " +
                                  "method 'getURL'" );
                    printStackTrace( e );
                    return null;
                }
            }
            else
            {
                // Inside the JAR
                url = getClass().getClassLoader().getResource(
                      SoundSystemConfig.getSoundFilesPackage() + filename );
            }
        }
        return url;
    }