创建列表深度副本

Question

我不确定我的问题是出在代码的深度复制部分，还是我在将元素添加到原始列表时犯了错误。到目前为止我所掌握的是：

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;
    }

...其中与此相关联的测试用例是：

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());
}

Answer 1

在构造函数Public OwnedPiggyBank（所有者所有者）中，您有

bank = new ArrayList<>();

因此，在deepcopybank中，是空的

assertEquals(coins, b.deepCopy());

更有意义

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