Multidimensional ArrayList in Java

Question

I'm simulating a supermarket, with various checkout lines, and each of them has its own queue, where the customers will be added when they finish shopping. Both customers and checkouts are clases, instantiated in the main class using Arraylists.

ArrayList<Customer> customerList=new ArrayList<Customer>(maxCustomers);
for (i=0;i<maxCustomers;i++){
    customerList.add(new Customer(randomItems, randomArrival);
}

I create the checkouts in a simmilar way.

Arraylist<Checkout>checkoutList=new ArrayList<Checkout>(maxCheckoutLines);
for (i=0;i<maxCheckoutLines;i++){
    checkoutList.add(new Checkout());
}

The problem here is that I want to create another ArrayList to simulate one queue in each checkout, where I will add the Customers when they finish shopping. I don't know if I should use a multidimensional ArrayList when creating the Checkouts, and I would like to know also how to operate with it when adding the Customers. Regards

It's usually better to use the interface List instead of ArrayList — TheEwook
– TheEwook, Commented May 18, 2014 at 9:05
TheEwook is saying that because it makes it easier to change your type of List later. Equally if the order of the list isn't important you should use the Collection interface so you can easily change between any collection later. So Collection<Customer> customers=new ArrayList<Customer>() — Richard Tingle
– Richard Tingle, Commented May 18, 2014 at 9:16
Also; I note you use new ArrayList<Customer>(maxCustomers); be aware that maxCustomers isn't actually the maximum. Its just the initial capacity of the ArrayList. It will automatically resize if you add more than that to it (think of it as an efficiency measure and nothing more) — Richard Tingle
– Richard Tingle, Commented May 18, 2014 at 9:17
So I will change it to List. What are its pros against ArrayList? And regarding to the maxCustomers, there will not be more Customers than that number, so it would not resize. — Tito Mc
– Tito Mc, Commented May 18, 2014 at 9:23

Islay · Accepted Answer · 2014-05-18 09:11:21Z

3

The class Checkout can contain a field of ArrayList<Customer> that you should add the customers to.

public class Checkout {
    public ArrayList<Customers> custList = new ArrayList<>();
    ....

public static void main(String[] args){
    ArrayList<Checkout> chkouts = new ArrayList<>();

    chkouts.add(new Checkout());
    chkouts.get(0).custList.add(new Customer());

edited May 18, 2014 at 9:11

answered May 18, 2014 at 9:03

Islay

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2 Comments

Tito Mc Over a year ago

I understand that with chkouts.get(0).custList.add(new Customer()); I will add the Customer to the queue in the first checkout, is it true?

Tito Mc Over a year ago

Ok, thank you for your help, at the moment is working this way.

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