Java Language Null Pointer Exception Error

Question

I am getting a Null Pointer Exception Error at line 23 and line 78 in Main and getRank() respectively. This occurred when I reorganized the code and made the method getRank(). This code compiled and ran previous to my moving the code to the getRank() method, and I believe this error is due to a variable not being initialized properly.

import java.io.*;
import java.util.*;

public class NameRecord
{
    private static String num, name = "dav";
    private static String [] fields;
    private static int [] yearRank;
    private static boolean match;
    private static int getInts, marker, year, max;

        public static void main( String[] args)
        {
            java.io.File file = new java.io.File("namesdata.txt");
            try
            {
                Scanner input = new Scanner(file);
                while (input.hasNext())
                {
                    String num = input.nextLine();
                    if(match = num.toLowerCase().contains(name.toLowerCase()))
                    {
                        getRank();//My Problem I believe
                        getBestYear(marker);
                        System.out.printf("%s     %d     %d\n",fields[0],year,max);
                    }
                }
            }
            catch(FileNotFoundException e)
            {
                System.err.format("File does not exist\n");
            }
        }



    public static int getRank()
    {
        fields = num.split(" ");
        max = 0;
        for (int i = 1; i<12; i++)
        {   
            getInts = Integer.parseInt(fields[i]);
            if(getInts>max)
            {
                max = getInts;
                marker = i;
            }
        }
        return max;
    }
}

David Rabinowitz · Accepted Answer · 2012-04-15 13:49:37Z

3

The global num is not initialized, and hence equals null. In mailn() you create a new local variable which is not exposed to getRank(). If you want to use it, pass it as parameter getRank(num)

answered Apr 15, 2012 at 13:49

David Rabinowitz

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2 Comments

Martijn Courteaux Over a year ago

He is only hiding the class member. And it is the class member which is not initialised, but the local variable is.

Lion Over a year ago

You were the first to answer +1.

assylias · Accepted Answer · 2012-04-15 13:51:36Z

1

Your problem is with num, you declare a local variable in main which hides your instance member:

String num = input.nextLine();

You probably meant:

num = input.nextLine();

answered Apr 15, 2012 at 13:51

assylias

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1 Comment

Richard Long Over a year ago

This was the problem, once I deleted String from that line of code, the code worked. Thank you.

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