Array from object in nested class

Question

I'm about to make a class about parsing, here's part of my code.

public class Parsing {

   //some other atributes here

   public class Pack {
       String type;
       int[] brand;
       int total;
   }

   Pack[] v = new Pack[25];    

   public void setpackType(int a, String b) {
       v[a].type = b;
   }

   public String getpackType(int a) {
       return v[a].type;
   }

   public int getpackTotal(int a) {
       return v[a].total;
   }

   public void setpackTotal(int a, int b) {
       v[a].total = b;
   }

   public void setpackBrand(int a, int b, int c) {
       v[a].brand[b] = c;
   }

and

   public final void process(String s) throws FileNotFoundException {
       Scanner scanner;
       scanner = new Scanner(new File(s));
       try {
           if (scanner.hasNext()) {
               int y = scanner.nextInt();
               int i = 1;
               while (i <= y) {
                   v[i] = new Pack();
                   setpackType(i, scanner.next());
                   setpackTotal(i, scanner.nextInt();
                   int k = 0;
                   while (k < hh) {
                       setpackBrand(i, k, scanner.nextInt());
                   k++;
                   }
                   i++;
               }
           }
       } finally{
           scanner.close();
       }
   }
}

It's compiled with no error but when I tried to run, I got this:

    Exception in thread "main" java.lang.NullPointerException
    at Parsing.setpackTotal(Parsing.java:112)
    at Parsing.process(Parsing.java:153)
    at Parsing.main(Parsing.java:202)

I already tested it line by line. setpackType works just fine!

But I don't understand why setpackTotal AND setpackBrand can't work.

Thank you so much for help :)

If i runs beyond 24 (the last index in v) you will get this exception. What is the value of y in process()? — Alexander Pavlov
– Alexander Pavlov, Commented Feb 27, 2012 at 12:03
If v is not null, then a must be different between the setpackTotal and setpackType calls. Add System.out.println calls to see the values, or debug through the code. — Paul Grime
– Paul Grime, Commented Feb 27, 2012 at 12:03
After reformatting your code - the i++ statement should be inside the while block. But that doesn't explain the NPE, here we have an infinite loop. — Andreas Dolk
– Andreas Dolk, Commented Feb 27, 2012 at 12:09
BTW - as the code you've shown, doesn't compile, it's hard to tell, if the problem is inside this draft/fragment or in the real code that we haven't seen yet... — Andreas Dolk
– Andreas Dolk, Commented Feb 27, 2012 at 12:11
y is 4. i++ actually is inside the while block. The whole code is pretty long, I can't put it here, I think :/ but it's compiled. — username10
– username10, Commented Feb 27, 2012 at 13:01

user130076 · Accepted Answer · 2012-02-27 12:03:04Z

2

Arrays in Java are zero indexed, try changing your i variable in your process method to begin from 0 instead:

int i = 0;
while ( ... ) { 
   ...
   i++;
}

answered Feb 27, 2012 at 12:03

user130076

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1 Comment

username10 Over a year ago

I changed it but there was not any different. But thank you for trying.

Community · Accepted Answer · 2017-05-23 12:27:30Z

0

Ignoring that is missing a ) here:

setpackTotal(i, scanner.nextInt();

The NullPointerException can be caused because of the scanner.nextInt().

Try to debug the scanner to solve the problem.

Also, Peter's answer resolves part of the problem.

edited May 23, 2017 at 12:27

CommunityBot

11 silver badge

answered Feb 27, 2012 at 14:11

falsarella

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Comments

falsarella · Accepted Answer · 2014-08-20 00:18:13Z

-1

You need to change setpackTotal() to:

public void setpackTotal(int a, int b) {
    v[a] = new Pack();
    v[a].total=b;
}

edited Aug 20, 2014 at 0:18

falsarella

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answered Feb 27, 2012 at 12:11

Ashwini Raman

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1 Comment

falsarella Over a year ago

he is doing this: v[i]=new Pack();. it would override the current instance!

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