the images are not loading

I’m sorry to say this, but there are simply so many things wrong with your code…

Lets start with:

• DON’T override any of the paint methods of a top level container. To start with, none of the top level containers are double buffered.
• Use light weight components instead of heavy weight components (use JFrame instead of Frame, use JPanel instead of Panel)…
• Use JPanel as your painting surface instead of the Frame, for the same reasons as stated above…
• As mentioned, you’re thread code was doing nothing (new Thread().start()).
• You had no paint code to actually paint the fishies onto the screen (yes your fish had paint code, but nothing was calling it).
• You random number generator doesn’t work. I got all the fish to swim exactly in the same place…
• You’re image loading code is wrong. Use ImageIO instead
• Don’t store the rectangle reference directly. The problem is, if the window is resized, the available bounds for the fish to swim in will change, even if they are contained to within the bounds of the aquarium, it’s possible for the location of the aquarium to have changed.
• As mentioed, you image paths are incorrect. You never include src in any path. Once deployed, the src path will no longer exist.

Here is my take…

Aquarium

public class Aquarium extends JPanel {

    public static final int NUMNBER_OF_FISHIES = 12;

    private BufferedImage masterFish;
    private Vector<Fish> fishes = new Vector<Fish>(NUMNBER_OF_FISHIES);
    private int sleepTime = 110;

    public Aquarium() {

        //set the title and assign tracker object

        try {
            masterFish = ImageIO.read(getClass().getResource("/gnome_panel_fish.png"));
        } catch (IOException iOException) {
            iOException.printStackTrace();
        }

        // This is a little cheat which means you only ever need one fish image
        // Basically it will flip the master along it's horizontal axies ;)
        BufferedImage flippedMaster = new BufferedImage(masterFish.getWidth(), masterFish.getHeight(), masterFish.getType());
        Graphics2D g2d = flippedMaster.createGraphics();
        g2d.setTransform(AffineTransform.getScaleInstance(-1, 1));
        g2d.drawImage(masterFish, -masterFish.getWidth(), 0, this);
        g2d.dispose();

        for (int index = 0; index < NUMNBER_OF_FISHIES; index++) {
            fishes.add(new Fish(masterFish, flippedMaster, this));
        }

        Thread background = new Thread(new Background());
        background.setDaemon(true);
        background.start();

    }

    public static void main(String ar[]) {

        EventQueue.invokeLater(new Runnable() {
            @Override
            public void run() {

                try {
                    UIManager.setLookAndFeel(UIManager.getSystemLookAndFeelClassName());
                } catch (ClassNotFoundException classNotFoundException) {
                } catch (InstantiationException instantiationException) {
                } catch (IllegalAccessException illegalAccessException) {
                } catch (UnsupportedLookAndFeelException unsupportedLookAndFeelException) {
                }

                JFrame frame = new JFrame("The Aquarium ");
                frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
                frame.setLayout(new BorderLayout());
                frame.add(new Aquarium());
                frame.setSize(400, 400);
                frame.setLocationRelativeTo(null);
                frame.setVisible(true);

            }
        });
    }

    @Override
    protected void paintComponent(Graphics g) {

        super.paintComponent(g);

        for (Fish fish : fishes) {
            fish.drawFishImage(g);
        }

    }

    protected class Background implements Runnable {

        @Override
        public void run() {

            while (true) {

                for (Fish fish : fishes) {
                    fish.swim();
                }

                try {
                    Thread.sleep(sleepTime);
                } catch (Exception e) {
                    System.out.println(e.getMessage());
                }
                repaint();
            }
        }
    }
}

Fish

public class Fish {

    private Component tank;
    private Image image1, image2;
    private Point location, velocity;
    private Random random;

    public Fish(Image image1, Image image2, Component tank) {
        random = new Random();
        this.tank = tank;
        this.image1 = image1;
        this.image2 = image2;
        this.location = new Point(
                        100 + (Math.abs(random.nextInt()) % 300),
                        100 + Math.abs(random.nextInt()) % 100);
        this.velocity = new Point(random.nextInt() % 8, random.nextInt() % 8);
        System.out.println(location);
    }

    public void swim() {

        Rectangle edges = tank.getBounds();

        //determine the optimum velocity to make the fish swim

        if (random.nextInt() % 7 <= 1) {
            velocity.x += random.nextInt() % 4;
            velocity.x = Math.min(velocity.x, 8);
            velocity.x = Math.max(velocity.x, -8);
            velocity.y += random.nextInt() % 4;
            velocity.y = Math.min(velocity.y, 8);
            velocity.y = Math.max(velocity.y, -8);
        }

        //add the velocity to the location of the fish to make it move

        location.x += velocity.x;
        location.y += velocity.y;

        if (location.x < edges.x) {
            location.x = edges.x;
            velocity.x = -velocity.x;
        }

        if ((location.x + image1.getWidth(tank)) > (edges.x + edges.width)) {
            location.x = edges.x + edges.width - image1.getWidth(tank);
            velocity.x = -velocity.x;
        }

        if (location.y < edges.y) {
            location.y = edges.y;
            velocity.y = -velocity.y;
        }

        if ((location.y + image1.getHeight(tank)) > (edges.y + edges.height)) {
            location.y = edges.y + edges.height - image1.getHeight(tank);
            velocity.y = -velocity.y;
        }
    }

    public void drawFishImage(Graphics g) {
        if (velocity.x < 0) {
            g.drawImage(image1, location.x, location.y, tank);
        } else {
            g.drawImage(image2, location.x, location.y, tank);
        }
    }
}