Using an Arraylist in the constructor

Question

I have a list of stock as a class and then a class of stores with the constructor shown below. The stores has an array list which links to the stock class.

How would I access the array list for a certain store?

E.G. If I pick the store argos I want all the stock that it has in it. Each store has its own stock

    public Store(int storeId, String name, String location){
      this.storeId = storeId;
     this.name = name;
     this.location = location;
      items = new ArrayList<Stock>();
     }

A private local variable with a getter?

Keppil
– Keppil

2013-05-01 14:16:38 +00:00
Commented May 1, 2013 at 14:16 — Keppil
– Keppil, Commented May 1, 2013 at 14:16

blackpanther · Accepted Answer · 2013-05-01 14:23:19Z

3

If each Store has it's own list of Stock items, then this will have to be an attribute, or a private instance variable, of the class Stock. The items of the Store can then be accessed using a getter, eg.

public class Store {
    private List<Stock> items;

    public Store(List<Stock> items){
        this.items = items;
    }

    public List<Stock> getStock(){ 
        // get stock for this Store object. 
        return this.items;
    } 
    public void addStock(Stock stock){
        this.getStock().add(stock);
    }
}

Then, you can access the items for an instance of Store using the getter for Stock items.

edited May 1, 2013 at 14:23

answered May 1, 2013 at 14:18

blackpanther

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Comments

duffymo · Accepted Answer · 2013-05-01 14:18:44Z

1

You can provide safe access this way, but it'd be better encapsulation if you didn't give users the keys to the store and return the stock list.

public class Store {
    private List<Stock> stock;

    public Store(List<Stock> stock) {
        this.stock = ((stock == null) ? new ArrayList<Stock>() : new ArrayList<Stock>(stock));
    }

   public List<Stock> getStock() {
       return Collections.unmodifiableList(this.stock);
   }
}

answered May 1, 2013 at 14:18

duffymo

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1 Comment

duffymo Over a year ago

I like blackpanther's answer the best. His "addStock" is the right idea.

Ben Green · Accepted Answer · 2013-05-01 14:20:24Z

1

To be honest, I would advise using a HashMap. Have each Store as the key, or store ID, and then have the list of Stock as the value. This would allow you to simply do:

Map storeMap = new HashMap<String, List<Stock>();
items = storeMap.get(key);

answered May 1, 2013 at 14:20

Ben Green

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Comments

patrick.elmquist · Accepted Answer · 2013-05-01 14:30:51Z

1

public class Store {
    private List<Stock> items;

    public Store(int storeId, String name, String location){
        this.storeId = storeId;
        this.name = name;
        this.location = location;
        items = new ArrayList<Stock>();
    }

    public List<Stock> getAllStock(){
        return this.items;
    }
}

edited May 1, 2013 at 14:30

answered May 1, 2013 at 14:25

patrick.elmquist

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Comments

blackpanther · Accepted Answer · 2013-05-02 15:20:42Z

0

There are many possibilities to set the list to the Store object and with a getter you can return the list back.

public Store(int storeId, String name, String location,ArrayList<Stock> list){
    this.storeId = storeId;
    this.name = name;
    this.location = location;
    this.items = new ArrayList<Stock>();  //or any possibility to set list
}

public ArrayList<Stock> getListOfStock(){
    return this.items;
}

edited May 2, 2013 at 15:20

blackpanther

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answered May 1, 2013 at 14:19

Suresh Atta

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