"Main" Java.lang NullPointerException Please Help

[lilyumestar]

This project is due by Tuesday and I haven't even gotten half of it done. Can anyone please help me with this Exception error? I've been trying to figure it out for several hours

Error Message

"Main" Java.lang NullPointerException
                 at Project1.sortingByZipCode<Project1.java:80>
                 at Project1.main<Project1.java:31>
 

Here is the Source Code

// StringTokenizerDemo2.java
 
import java.util.StringTokenizer;
import javax.swing.JOptionPane;
 
 
public class Project1 
{
 
       public static void main(String[] args)
       {
          final int MAX_NUMBER_OF_NUMBERS = 40;
 
          if ( args.length == 0 )
          {
             System.out.println("This program sorts short integers");
             System.out.println("from the file specified by a");
             System.out.println("command-line argument.");
             System.exit(0);
          } // if
 
          final String inputFileName = args[0];
          final String outputFileName = "sorted-" + inputFileName;
 
          String[] numbersArray = new String[MAX_NUMBER_OF_NUMBERS];
 
          // Read numbers into numbersArray from input file:
          int subArrayLength = readFile(inputFileName, numbersArray);
 
          //Sorts the zipcode by compareTo method
          sortByZipCode(numbersArray, subArrayLength);
 
 
        }  // method main
 
 
 
 
 
   private static int readFile(String filename, String[] capacities)
   {
           TextFileInput in = new TextFileInput(filename);
 
           // Read capacities into array:
           int lengthFilled = 0;
           String line = in.readLine();   // read first line in file
           while ( lengthFilled < capacities.length && line != null )
               {
 
                   line = in.readLine();       // read next line in file
                   lengthFilled++;
               } // while
 
           // Check to see if all the capacities in the file were read.
           // If not, then the array wasn't big enough to hold them all.
           // In that case, print an error message and quit.
           if ( line != null )            // i.e. if end-of-file not reached
           {
                   System.out.println("File contains too much capacity.");
                   System.out.println("This program can process only "
                           + capacities.length + " capacities.");
                   System.exit(1);
           }  // if
 
           // Release file for re-use:
           in.close();
 
           return lengthFilled;
       }  // method inputFromFile
 
 
 
 
   private static void sortByZipCode (String[] lines, int length) 
   { 
           for ( int i = 0; i < length-1; i++ ) 
           { 
               for ( int j = i + 1; j < length; j++ ) 
               {
                   if ( lines[j].compareTo(lines[i]) > 0 ) 
                   {
                           String Temp = lines[i];
                           lines[i] = lines[j];
                           lines[j]= Temp;
                   }
 
               }//for loop with the j 
 
           }//for loop with the i
   }//Method SortByZipCode
}//Project1

[JosAH]

You don't fill your array when you're reading the file content. All you do is check
whether or not your aray is large enough to store the entire content of the file.

When the method is finished all the entries in the array are still all null and your
sorting method doesn't like that; hence the NullPointerException.

kind regards,

Jos

[lilyumestar]

Thank you very much for the help. It turned out that I didnt store my lines into the array. THank you.