ArrayList Problem (java.lang.NullPointerException)

[kgvnova]

package isbnchecker;

import java.io.FileNotFoundException;
import java.io.FileReader;
import java.util.ArrayList;
import java.util.Scanner;
import java.util.logging.Level;
import java.util.logging.Logger;

public class ISBNReader {
    
    private ISBN isbn = new ISBN();
    private ArrayList<String> inISBN = new ArrayList<String>();
    private String fileName = "";
    private String next = "";

    public ISBNReader(){
        this.isbn = null;
        this.inISBN = null;
    }

    public void setFileName(String fileName){
        this.fileName = fileName;
    }

    public String getFileName(){
        return fileName;
    }
    
    public void setISBNNumbers(){
        try{
            FileReader fr = new FileReader(fileName);
            Scanner in = new Scanner(fr);
            
            while(in.hasNext())
 [COLOR="Red"]               [B]inISBN.add(in.next());  [/B][/COLOR] 
        }
        catch(FileNotFoundException ex){
            Logger.getLogger(ISBNReader.class.getName()).log(Level.SEVERE, null, ex);
        }
            
    }
    
    public ArrayList<String> getISBNNumbers(){
        return inISBN;
    }
}

Exception in thread "main" java.lang.NullPointerException
at isbnchecker.ISBNReader.setISBNNumbers(ISBNReader.java:43)
at isbnchecker.Main.main(Main.java:34)
Java Result: 1

Hey everyone, I am currently working on this programming assignment for my computer science class and am having some trouble with an arraylist in the code above (the line in red). I can't seem to figure out what is causing the error I keep receiving. Any suggestions?

Thanks!

[Fou-Lu]

inISBN has been set to null in the constructor.

[kgvnova]

Finishing the Project

Thank you, I realized what i had done right after I posted that. However, I've run in to another problem within my program that I can't seem to figure out. I keep receiving the error below:

Exception in thread "main" java.lang.NumberFormatException: For input string: "978-0-13-601722-6"
at java.lang.NumberFormatException.forInputString(NumberFormatException.java:48)
at java.lang.Integer.parseInt(Integer.java:458)
at java.lang.Integer.parseInt(Integer.java:499)
at isbnchecker.ISBN.stringToNumbers(ISBN.java:49)
at isbnchecker.ISBNReader.setISBNNumbers(ISBNReader.java:44)
at isbnchecker.Main.main(Main.java:35)
Java Result: 1
BUILD SUCCESSFUL (total time: 0 seconds)

The program is supposed to read in a text file of ISBN numbers and check if they are valid, and then print out the list of valid, or invalid numbers.
Here are all my classes:

public class Main {

    /**
     * @param args the command line arguments
     */
    public static void main(String[] args) {
        ISBN isbn = new ISBN();
        ISBNReader reader = new ISBNReader();
        ISBNProcessor processor = new ISBNProcessor(reader, isbn);
        ISBNPrinter printer = new ISBNPrinter(processor);


        Scanner scan = new Scanner(System.in);
        reader.setFileName("isbn.txt");

        reader.setISBNNumbers();
        processor.processISBNNumbers();
        System.out.println(reader.getISBNNumbers());
        printer.printISBNNumbers();
    }

}

package isbnchecker;

import java.io.FileNotFoundException;
import java.io.FileReader;
import java.util.ArrayList;
import java.util.Scanner;
import java.util.logging.Level;
import java.util.logging.Logger;

public class ISBNReader {
    
    private ISBN isbn = new ISBN();
    private ArrayList<ISBN> inISBN = new ArrayList<ISBN>();
    private String fileName = "";
    private String next = "";

    public ISBNReader(){
    }

    public void setFileName(String fileName){
        this.fileName = fileName;
    }

    public String getFileName(){
        return fileName;
    }
    
    public void setISBNNumbers(){
        try{
            FileReader fr = new FileReader(fileName);
            Scanner in = new Scanner(fr);
            while(in.hasNextLine())
                next = in.next();
                isbn.setISBNString(next);
                isbn.stringToNumbers();
                inISBN.add(isbn);
        }
        catch(FileNotFoundException ex){
            Logger.getLogger(ISBNReader.class.getName()).log(Level.SEVERE, null, ex);
        }
            
    }
    
    public ArrayList<ISBN> getISBNNumbers(){
        return inISBN;
    }
}

import java.util.ArrayList;

public class ISBNProcessor {
    
    private ISBNReader reader = new ISBNReader();
    private ISBN isbn = new ISBN();
    private String numOnlyString;
    private ArrayList<ISBN> inISBN = new ArrayList<ISBN>();
    private ArrayList<ISBN> validISBNs = new ArrayList<ISBN>();
    private ArrayList<ISBN> invalidISBNs = new ArrayList<ISBN>();
    private boolean isNumOnly;
    private int[] isbnNums = new int[13];
    
    ISBNProcessor(ISBNReader reader, ISBN isbn){
        this.reader = reader;
        this.isbn = isbn;
        inISBN = reader.getISBNNumbers();
    }
    
    public void processISBNNumbers(){
        for(int i = 0; i <inISBN.size();i++){
            isbnNums = inISBN.get(i).getISBNNumbers();
            if(isbnNums[12] == (10 - ((isbnNums[0] + 3*isbnNums[1] +isbnNums[2] + 3*isbnNums[3] +
                                       isbnNums[4] + 3*isbnNums[5] +isbnNums[6] + 3*isbnNums[7] +
                                       isbnNums[8] + 3*isbnNums[9] +isbnNums[10] + 3*isbnNums[11])
                                       % 10) % 10)){
                validISBNs.add(inISBN.get(i));
            }
            else{
              invalidISBNs.add(inISBN.get(i));
            }
        }
    }

    public ArrayList<ISBN> getValidISBNNumbers(){
        return validISBNs;
    }

    public ArrayList<ISBN> getInvalidISBNNumbers(){
        return invalidISBNs;
    }

}

public class ISBNPrinter {
    
    private ISBNReader reader = new ISBNReader();
    private ISBN isbn = new ISBN();
    private ISBNProcessor processor = new ISBNProcessor(reader, isbn);;

    ISBNPrinter(ISBNProcessor processor){
        this.processor = processor;
    }

    public void printISBNNumbers(){
        System.out.println("Valid");
        for(int i = 0; i < processor.getValidISBNNumbers().size(); i++){
            System.out.println(processor.getValidISBNNumbers().get(i).getISBNString());
        }

        System.out.println("Invalid");
        for(int i = 0; i < processor.getInvalidISBNNumbers().size(); i++){
            System.out.println(processor.getInvalidISBNNumbers().get(i).getISBNString());
        }
    }
}

public class ISBN {

    private int[] isbnNumbers = new int[13];
    private String isbnString;


    public ISBN(int[] isbn){
        this.isbnNumbers = isbn;
    }

    ISBN() {
    }

    public void setISBNNumbers(int[] isbn){
        this.isbnNumbers = isbn;
    }

    public int[] getISBNNumbers(){
        return this.isbnNumbers;
    }

    public void setISBNString(String isbnString){
        this.isbnString = isbnString;
    }

    public String getISBNString(){
        return this.isbnString;
    }

    public void stringToNumbers(){
        for(int i = 0; i < isbnString.length(); i++){
            if(Integer.parseInt(isbnString.substring(i,i+1)) == 1 ||Integer.parseInt(isbnString.substring(i,i+1)) == 2 ||
               Integer.parseInt(isbnString.substring(i,i+1)) == 3 ||Integer.parseInt(isbnString.substring(i,i+1)) == 4 ||
               Integer.parseInt(isbnString.substring(i,i+1)) == 5 ||Integer.parseInt(isbnString.substring(i,i+1)) == 6 ||
               Integer.parseInt(isbnString.substring(i,i+1)) == 7 ||Integer.parseInt(isbnString.substring(i,i+1)) == 8 ||
               Integer.parseInt(isbnString.substring(i,i+1)) == 9 ||Integer.parseInt(isbnString.substring(i,i+1)) == 0){

                    isbnNumbers[i] = (int) Integer.parseInt(isbnString.substring(i));
            }
            else{

            }

        }
    }
}

Any help on finishing this program would be greatly appreciated, as it is due at midnight tonight, and i am struggling at this point

Thanks!

[Gox]

Only took a very quick look but my guess is the way stringToNumbers() is written.

Given this string 978-0-13-601722-6 you are trying to take each character in the string and convert to a int; one by one. However, Java doesn't doesn't know how to convert a "-" to an int and is throwing a numberFormatException.

You'll need to figure out a way to handle this. Remove the "-"'s from the string, or check that for the character being a "-" and then not trying to convert to an int are a couple possibilities.

[kgvnova]

Ok I think i solved that problem. I removed the stringToNumbers method in ISBN and changed the setISBNNumbers in ISBNReader, so it reads in the ISBN numbers in a second time but this time only as ints. The setISBNNumbers now looks like this:

    public void setISBNNumbers(){
        try{
            FileReader fr = new FileReader(fileName);
            Scanner in = new Scanner(fr);
            while(in.hasNextLine()){
                next = in.next();
                isbn.setISBNString(next);
                inISBN.add(isbn);
            }
            in.close();
            Scanner scanNums = new Scanner(fr);
            while(scanNums.hasNextLine()){
                for(int i = 0; i < 13; i++){
                    isbnNums[i] = scanNums.nextInt();
                }
            }
            scanNums.close();
        }
        catch(FileNotFoundException ex){
            Logger.getLogger(ISBNReader.class.getName()).log(Level.SEVERE, null, ex);
        }      
    }

However, I now receive a result that only reports the final ISBN number in the invalid list. The results look like this:
Valid
Invalid
978-0-13-601722-6
978-0-13-601722-6
978-0-13-601722-6
978-0-13-601722-6
978-0-13-601722-6
978-0-13-601722-6

The text file contains the following:
978-04-2135-828-8
978-03-2135-828-8
97A-03-2135-828-8
978-1408819899
978-0-13-216675-1
978-0-13-601722-6

Any suggestions?