Array throwing exception - arrays

Question

I can't seem to put my finger on this and why the array is not being initialized.
Basically I am coding a 2d top down spaceship game and the ship is going to be fully customizable. The ship has several allocated slots for certain "Modules" (ie weapons, electronic systems) and these are stored in an array as follows:
protected Array<Weapon> weaponMount;
Upon creating the ship none of the module arrays are initialized, since some ships might have 1 weapon slot, while others have 4.
So when I code new ships, like this example:
public RookieShip(World world, Vector2 position) {
this.width = 35;
this.height = 15;
// Setup ships model
bodyDef.type = BodyType.DynamicBody;
bodyDef.position.set(position);
body = world.createBody(bodyDef);
chassis.setAsBox(width / GameScreen.WORLD_TO_BOX_WIDTH, height / GameScreen.WORLD_TO_BOX_HEIGHT);
fixtureDef.shape = chassis;
fixtureDef.friction = 0.225f;
fixtureDef.density = 0.85f;
fixture = body.createFixture(fixtureDef);
sprite = new Sprite(new Texture(Gdx.files.internal("img/TestShip.png")));
body.setUserData(sprite);
chassis.dispose();
// Ship module properties
setShipName("Rookie Ship");
setCpu(50);
setPower(25);
setFuel(500);
setWeaponMounts(2, world);
setDefenseSlots(1);
addModule(new BasicEngine(), this);
addModule(new BasicBlaster(), this);
// Add hp
setHullHP(50);
setArmorHP(125);
setShieldHP(125);
}
#Override
public void addModule(Module module, Ship currentShip) {
// TODO Auto-generated method stub
super.addModule(module, currentShip);
}
#Override
public void setWeaponMounts(int weaponMounts, World world) {
weaponMount = new Array<Weapon>(weaponMounts);
// super.setWeaponMounts(weaponMounts, world);
}
#Override
public String displayInfo() {
String info = "Everyones first ship, sturdy, reliable and only a little bit shit";
return info;
}
When I set the number of weapon mounts the following method is called:
public void setWeaponMounts(int weaponMounts, World world) {
weaponMount = new Array<Weapon>(weaponMounts);
}
This basically initializes the array with a size (weapon mounts available) to whatever the argument is. Now to me this seems fine but I have setup a hotkey to output the size of the Array, which reports zero. If I try to reference any objects in the array, it throws an outofbounds exception.
The addModule method adds to the array as follows:
public void addModule(Module module, Ship currentShip) {
currentShip.cpu -= module.getCpuUsage();
currentShip.power -= module.getPowerUsage();
if(module instanceof Engine){
engine = (Engine) module;
}else if(module instanceof Weapon){
if(maxWeaponMounts == weaponMount.size){
System.out.println("No more room for weapons!");
}else{
maxWeaponMounts += 1;
weaponMount.add((Weapon)module);
}
}
}
My coding ain't great but heh, better than what I was 2 month ago....
Any ideas?

Answer 1

First of all, You should avoid instanceof. It's not a really big deal performance-wise, but it always points to problems with your general architecture. Implement two different addModule methods. One that takes a Weapon, and one that takes an Engine.
Now back to topic:
else if(module instanceof Weapon){
if (maxWeaponMounts == weaponMount.size) {
System.out.println("No more room for weapons!");
} else{
maxWeaponMounts += 1;
weaponMount.add((Weapon)module);
}
}
It looks like you use maxWeaponMounts as a counter instead of a limit. That's why I assume that it will initially be 0. The same holds for Array.size. It is not the limit, but size also counts how many elements the Array currently holds. Thus you will always have (maxWeaponMounts == weaponMount.size) as 0 == 0 and you will not add the weapon to the array. It will always stay empty and trying to reference any index will end in an OutOfBoundsException.
What you should actually do is using maxWeaponMounts as a fixed limit and not the counter.
public void setWeaponMounts(int weaponMounts, World world) {
weaponMount = new Array<Weapon>(weaponMounts);
maxWeaponMounts = weaponMounts;
}
else if(module instanceof Weapon){
if (weaponMount.size >= maxWeaponMounts) {
System.out.println("No more room for weapons!");
} else{
weaponMount.add((Weapon)module);
}
}