Question

I have three methods with duplicated code.
The first two methods are nearly completely duplicated. The third one differs a bit as for fires more information should be drawn.

I want to remove this duplicated code and thought about the template method pattern using inner classes. Is this the right way to go or is there a better solution?

private void drawWaterSupplies(Graphics g) {
    double hScale = getWidth() / (double) groundMap.getWidth();
    double vScale = getHeight() / (double) groundMap.getHeight();

    int imageOffsetX = waterSupplyImage.getWidth() / 2;
    int imageOffsetY = waterSupplyImage.getHeight() / 2;
    for (Location l : groundMap.getWaterSupplyLocations()) {
        int x = (int) (l.getX() * hScale);
        int y = (int) (l.getY() * vScale);

        g.drawImage(waterSupplyImage, x - imageOffsetX, y - imageOffsetY,
                null);
    }
}

private void drawEnergySupplies(Graphics g) {
    double hScale = getWidth() / (double) groundMap.getWidth();
    double vScale = getHeight() / (double) groundMap.getHeight();

    int imageOffsetX = energySupplyImage.getWidth() / 2;
    int imageOffsetY = energySupplyImage.getHeight() / 2;
    for (Location l : groundMap.getEnergySupplyLocations()) {
        int x = (int) (l.getX() * hScale);
        int y = (int) (l.getY() * vScale);

        g.drawImage(energySupplyImage, x - imageOffsetX, y - imageOffsetY,
                null);
    }
}

private void drawFires(Graphics g) {
    double hScale = getWidth() / (double) groundMap.getWidth();
    double vScale = getHeight() / (double) groundMap.getHeight();

    int imageOffsetX = fireImage.getWidth() / 2;
    int imageOffsetY = fireImage.getHeight() / 2;
    for (Fire fire : groundMap.getFires()) {
        Location l = fire.getLocation();
        int x = (int) (l.getX() * hScale);
        int y = (int) (l.getY() * vScale);

        g.drawImage(fireImage, x - imageOffsetX, y - imageOffsetY, null);
        // TODO: draw status bar showing state of fire below
    }
}

Answer 1

It seems to me your collection of objects (Fire, WaterSupply etc.) aren’t as clever as they should be. Ideally you should be able to say:

for (Fire f : groundMap.getFires()) {
   f.draw(g);
}

and each object would be able to locate itself (using its location), size itself (since a Fire knows it’s going to use a FireImage etc.) and draw itself onto the provided Graphics object.

To take this further, I would expect to pass a Graphics object to your groundMap thus:

groundMap.drawFires(g);

The idea is that in OO you shouldn’t ask objects for their details and then make decisions. Instead you should tell objects to do things for you.