CODEWITHSUNDEEP
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Jeremy Eisner
Jeremy Eisner

Reputation: 51

Creating a List deep copy

I'm trying to create a deep copy of a List but I keep getting the error that the new list is empty <[]> even after trying everything to copy the original list.

I'm not sure if my problem lies in the deep copy section of the code or if I made a mistake when adding the elements to the original list. What I have so far is:

public class OwnedPiggyBank 
{
    List<Coin> bank;
    private Owner owner;


    public OwnedPiggyBank(Owner owner) 
    {
        this.owner = owner;
        bank = new ArrayList<>();
    }

    public void add(List<Coin> coins) 
    {
        bank.addAll(coins);
    }

    public List<Coin> deepCopy() 
    {
        List<Coin> coins = new ArrayList<>();

        for (Coin c : bank)
        {
            coins.add(new Coin(c));
        }

        return coins;
    }

... where the test case associated with this is:

public void test() 
{
    OwnedPiggyBank b = new OwnedPiggyBank("Lola");
    List<Coin> coins = new ArrayList<Coin>(Arrays.asList(Coin.PENNY, Coin.LOONIE, Coin.TOONIE));
    b.add(coins);
    OwnedPiggyBank c = new OwnedPiggyBank(b);
    assertEquals(coins, c.deepCopy());
}

Upvotes: 0

Views: 104

Answers (2)

user54321
user54321

Reputation: 632

OwnedPiggyBank doesn't seem to have a constructor that takes in another OwnedPiggyBank as called in 4th statement of the written test case. Adding a constructor like below should fix the issue.

OwnedPiggyBank(OwnedPiggyBank ob){
   this.owner = ob.owner;
   this.bank = ob.deepCopy();
}

Upvotes: 1

Scary Wombat
Scary Wombat

Reputation: 44844

In your constructor public OwnedPiggyBank(Owner owner) you have

bank = new ArrayList<>();

so of course in deepCopy bank is empty

assertEquals(coins, b.deepCopy());

makes more sense

If you wanted to keep the test case, then you need to do something like

public OwnedPiggyBank(OwnedPiggyBank owner) 
{
    this.owner = owner;
    bank = owner.deepCopy();
}

Upvotes: 2

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