如何有效地将数组更改为arraylist

Question

I have array variable declared like this:

public class carshop {
    int numofcars = 0;
    int maxcars = 10;
    ACar[] allCars;
    private CarShop;

public CarShop() { //Car Constructor
    maxcars = maxE;
    allCars = new ACar[maxcars];
    }
}

In my coding example, every time a user adds a new car (via string input), it will increase the numofcars by 1. I have tried changing the array type into a arraylist

ArrayList<ACar> allCars = new ArrayList<ACar>(Arrays.asList());

I changed the allCars = new ACar[maxcars]; line into this: allCars = ACar.add(maxcars);

However now eclipse is giving me errors saying "The method add(int) is undefined for the type ACar".

Can you tell me what I have done wrong? Sorry if I have explained this poorly.

Answer 1

ACar is an array so it doesn't have the add() method and you need to insert values by doing ACar[x] = value;

If you want to easily convert an array to a List you can just do:

List<ACar> carList = Arrays.asList(allCars);

or for ArrayList specifically:

ArrayList<ACar> carList = new ArrayList<ACar>(Arrays.asList(allCars));

However you should also think about why you have both an array and an ArrayList. You could instead just be doing:

List<ACar> carList = new ArrayList<ACar>(maxCars);

The maxCars variable is optional, you don't need to set the initial size of an ArrayList unless you are trying to optimise the code.