array.length throwing NullPointerException in junit but not when the application is run

Question

I am running into an odd problem. I am still new to coding so this may stem from my misunderstanding the nature of arrays. My problem is this: I am attempting to write unit tests for some arrays in my application in which I call arr.length which then throws an NPE. The arrays are initialized in the constructor of the class so that's not the problem. I have tried initializing them with values at each index to see if that changed anything but it does not. What is confusing me the most is that when I call arr.length on the same array when just running the application I get a value.

Is there something about JUnit I'm missing?

The method being tested is incomplete. I was in the middle of writing it when I started encountering the NPE so I never actually got to the code that assigns the values to the array. Here is the test and the class being tested:

@Test
void testCFArray() throws IOException {
    WebReaderFilter adder = new WebReaderFilter();
    Stock stock = new Stock("INTC");
    stock.setProfile(adder.getStockDetails(stock.getTicker()));

// This method call throws the NPE

    stock.setArrays(stock.getProfile());
    BigInteger[] arr = stock.getCashFlowArray();
    assertEquals(BigInteger.valueOf(33145000000L), arr[0]);
}

package companyValueModel;

import java.math.BigDecimal;
import java.math.BigInteger;
import java.util.HashMap;

public class Stock {

    private String ticker;
    private BigDecimal currentPrice;

    private BigInteger[] freeCashFlow;
    private BigInteger[] cashFlow;
    private BigInteger[] debt;
    private BigDecimal[] divPerShare;

/*
 * Keys: [companyName], [EBITDA], [Enterprise Value], [description], [industry],
 * [yearHigh], [price], [Total shareholders equity], [Goodwill and Intangible
 * Assets], [Capital Expenditure], [sector], [yearLow], [marketCap], [Dividend
 * payments], [ticker], [Revenue Growth], [Cash and short-term investments],
 * [Net Income], [Revenue]
 * 
 * Array keys: [Long-term debt-1], [Free Cash Flow0], [Long-term debt-2],
 * [Long-term debt0], [Free Cash Flow-2], [Dividend per Share0], [Free Cash
 * Flow-1], [Dividend per Share-1], [Operating Cash Flow0], [Operating Cash
 * Flow-1], [Operating Cash Flow-2]
 * 
 * keys with numbers at the end represent (0) = this year, (-1) = year prior,
 * etc.
 */

    private HashMap<String, String> profile;

    public Stock(String ticker) {
        this.ticker = ticker;
    }

    public Stock(HashMap<String, String> profile) {
        this.profile = profile;
        this.ticker = profile.get("ticker");
        freeCashFlow = new BigInteger[3];
        cashFlow = new BigInteger[3];
        debt = new BigInteger[3];
        divPerShare = new BigDecimal[2];
    }

    public HashMap<String, String> getProfile() {
        return profile;
    }

    public void setProfile(HashMap<String, String> profile) {
        this.profile = profile;
    }

    public String getTicker() {
        return ticker;
    }

    public void setCurrentPrice(BigDecimal price) {
        currentPrice = price;
    }

    public BigDecimal getCurrentPrice() {
        return currentPrice;
    }

    public void setArrays(HashMap<String, String> profile) throws NumberFormatException {
        int j = 0;
//      this line throws the NPE.  It disappears if I replace cashFlow.length with 3

        for (int i = 0; i < cashFlow.length; i++) {

//          This line was to verify that the key existed (it does)

            System.out.println(profile.get("Operating Cash Flow" + j));

//          also as an aside if anybody could tell me whether I'm parsing this string properly to bigInt I would appreciate it.

            double flow = Double.parseDouble(profile.get("Operating Cash Flow" + j));
            BigInteger cf = BigInteger.valueOf((long) flow);
            j--;

// Here is where the assigning code would have gone

        }
    }

    public BigInteger[] getCashFlowArray() {
        return cashFlow;
    }

    public BigInteger[] getFreeCashFlowArray() {
        return freeCashFlow;
    }

    public BigInteger[] getDebtArray() {
        return debt;
    }

    public BigDecimal[] getDivPerShare() {
        return divPerShare;
    }
}

It has occurred to me that I could write a similar method with constants for the unit test and use another for the program but that would leave that method without a proper unit test which does not tickle my fancy. In the end the arrays may not be necessary but I think they be convenient later. I'm asking to further my understanding so that if I run into this issue again I know what needs to be done.

Answer 1

The String-argument constructor is used by you, while creating Stock object in test case.

--> Initialize cashFlow in that..

public Stock(String ticker) {
    this.ticker = ticker;
    cashFlow = new BigInteger[3]; // add this
}

OR

--> Use the other HashMap argument constructor while initializing Stock object in test case.