Question

I coded up a class which models a stock:

public Stock(String ticker, int shares, float purchasePrice) throws IllegalArgumentException
{
    if(ticker == null || ticker == "" ||
        shares <= 0 || purchasePrice <= 0)
        throw new IllegalArgumentException(Messages.enterAppropriateValues());

    this.ticker = ticker;
    this.shares = shares;
    this.purchasePrice = purchasePrice;
    latestPrice = purchasePrice;
    updatePercentGain();
}

The copy-constructor looks like:

public Stock(Stock other) throws IllegalArgumentException
{
    this(other.ticker, other.shares, other.purchasePrice);
}

Here are the commands I that used to test this:

    Stock bac = new Stock("BAC", 100, 42.22f);
    System.out.println(bac);

    bac.setLatestPrice(43.35f);
    System.out.println(bac);

    Stock bacCopy = new Stock(bac);
    System.out.println(bacCopy);

Output is:

    BAC 100 42.22 42.22 0.00%
    BAC 100 42.22 43.35 2.68%
    BAC 100 42.22 42.22 0.00%

For some reason, the last value which represents the percent-gain is not copying over?

Here’s the percent-gain method btw:

public void updatePercentGain()
{
    percentGain = ((latestPrice - purchasePrice) / purchasePrice) * 100;
}

Where am I going wrong?

Answer 1

When your Stock constructor runs, it initialises the latestPrice with the purchasePrice passed in to the constructor. Since these values are the same, the percent gain will be 0.00%.

If you wish to also copy the current latestPrice in your copy constructor, you’ll have to do that too:

public Stock(Stock other) throws IllegalArgumentException
{
    this(other.ticker, other.shares, other.purchasePrice);
    this.latestPrice = other.latestPrice;
    updatePercentGain();
}