What is the reason for this Java NullPointerException?

Question

I seem to get a NullPointerException in my code at line 15, but I just cannot understand why. I have been stuck on this for some hour now, and I don't know how to fix it. I have read up on what NullPointerException is, and I think I have a clear grasp of what it is, but I thought my if-statement would fix it, but apparently not.

Here is the code:

package learning;
import java.io.BufferedReader;
import java.io.File;
import java.io.FileNotFoundException;
import java.io.FileReader;
import java.io.IOException;
import java.util.Scanner;
public class Index{
    public static void main(String args[]){
        Index indexObject = new Index();
        String filePath = "C:\\Users\\Edvin\\Desktop\\inputPrices.txt";
        Scanner inputScanner = new Scanner(System.in);
        int average = 0;
        if(indexObject != null){
            average = indexObject.findAverage(getFileInfo(filePath).split(","));
        }
        else{
            System.out.println("Object instance is null. Terminating program.");
        }

        int currentItemInput = inputScanner.nextInt();
        if(currentItemInput<average && currentItemInput != 0){

        }
    }

    private static String getFileInfo(String x){
        File listOfPrices = new File(x);
        String error = "An error occurred";
        try{
            BufferedReader getInfo = new BufferedReader(new FileReader(listOfPrices));

            String prices = getInfo.readLine();

            while(prices != null){
                prices = getInfo.readLine();
            }
            return prices;
        }
        catch(FileNotFoundException e){
            System.out.println("Couldn't find File");
            System.exit(0);
            return error;
        }
        catch(IOException e){
            System.out.println("An I/O error occurred");
            System.exit(0);
            return error;
        }
    }

    public int findAverage(String[] tempIndivPrices){
        int x = 0;
        int y = 0;
        int total;
        int [] indivIntPrices = null;
        for(String i : tempIndivPrices){
            indivIntPrices[x] = Integer.parseInt(tempIndivPrices[x]);
            x++;
        }
        for (int element : indivIntPrices){
            total =+ indivIntPrices[element];
            if(element==indivIntPrices.length-1){
                int result = total / indivIntPrices.length;
                System.out.println(result);
                return result;
            }
        }
        return 0;
    }
}

No stacktrace needed. Why do you think `int [] indivIntPrices = null;` is going to work? — ApproachingDarknessFish, Aug 22 '14 at 23:29
Your line contains too much methods calls to clearly see the problems. Change your code (temporarily) so that you call only one method by line, and you'll know exactly whre is the issue. — Dici, Aug 22 '14 at 23:31

score 2 · Answer 1 · edited Aug 23 '14 at 10:55

2

You are declaring an array but you initialize it to null in this line: int [] indivIntPrices = null;

indivIntPrices is now a null pointer. You are then trying to access this array two lines later indivIntPrices[x] = ... which is not going to work because the variable is not pointing to an array.

To solve this, allocate a new array of integers with the same size as the input array:

int [] indivIntPrices = new int[tempIndivPrices.length];

edited Aug 23 '14 at 10:55

Boann

48,794
16
117
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answered Aug 22 '14 at 23:32

Philipp

67,764
9
118
153

2

tempIndivPrices.length would look cleaner imo. – nmore Aug 23 '14 at 00:24

score 1 · Answer 2 · answered Aug 22 '14 at 23:29

1

Try to check this part of the code: getFileInfo(filePath)

Are you getting the properly result of it? It's the only part that you can get this error.

answered Aug 22 '14 at 23:29

vinibarr

500
3
5

score 0 · Answer 3 · edited Aug 23 '14 at 01:47

0

Remove this loop:

while(prices != null){
    prices = getInfo.readLine();
}

Then, it works.

edited Aug 23 '14 at 01:47

AstroCB

12,337
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answered Aug 23 '14 at 01:03

harish

1

What is the reason for this Java NullPointerException?

3 Answers3