help with global array

[Jeff Yan]

Hey all, im having a little trouble. basically im reading an array of integers from a file and putting it into a linked list, then from the linked list im transfering it to an array using the .toArray() method of the arrayList methods. the array is filled with the data, but when i call another method to display the array it is coming up with a null pointer error. ive used System.out.println to test it and the array is of the correct size, and with the correct data in it in the method that reads the data into it, but outside of it the array is "empty" even though it is a global array?! it compiles absolutly fine but with a unsafe operation warning but that is not the issue. my code is below! much appriciated. Jeff.

import java.io.*;
import java.util.*;
import java.lang.*;
/**
 * Methods to sort an array of integers
 * Stephen John Smith
 * Student Number 081202809
 * Version 1.0
 */
public class Sort
{
    // instance variables
    int count = 0;
    ArrayList tempData = new ArrayList  ();
    int data[];
    
    public void readFile() throws FileNotFoundException, IOException
    {
            try
            {
                // file reader to read file one line at a time getting file from selection user inputted
                FileReader input = new FileReader(chooseTest());
            
                //buffer reader to filter filereader through to read line at a time
                BufferedReader bufRead = new BufferedReader (input);
            
                //variable to hold current line
                String line;
            
                //read first line
                line = bufRead.readLine ();
                
                //put data into array changing string into integer
                 if (isParsableToInt(line) == true)
                 {
                      int temp = Integer.parseInt(line);
                      tempData.add(temp);
                 }
                 
                 while (line != null)
                 {
                     for (int i = 1; line != null; i++)
                     {
                            line = bufRead.readLine();
                            if (isParsableToInt(line) == true)
                            {
                                int temp = Integer.parseInt(line);
                                tempData.add(temp);
                                break;
                            }
                     }
                 }
            }
            //catch exeptions
            catch (ArrayIndexOutOfBoundsException e)
            {
                System.out.println("Java File Read Error! Check input file location.");
            }
            
            catch (IOException e)
            {
                System.out.println("Unknown error has occured!");
            }
            
            //switchs informatioin from the arrayList to the array for sorting
            Object data[] = tempData .toArray();
            System.out.println(data.length);
            showContents();
            
     }
      
     //method to choose which test file to use
     private  String chooseTest () throws IOException
     {
        String Option;  
        BufferedReader reader;  
        reader = new BufferedReader(new InputStreamReader (System.in));  
                                       
         System.out.println("Choose test file to use:\n\nFor test file 1 enter 1\nFor test file 2 enter 2\nFor test file 3 enter 3\nFor test file 4 enter 4\n\nYour selection is: ");  
        
         Option=reader.readLine();  
         System.out.println("\nYou chose test file " + Option + "\n");
         if(Option.equals("1"))
         {  
            Option = "test1.txt";
         }  else if (Option.equals("2"))
         {
            Option = "test2.txt";
          }else if (Option.equals("3"))
          { 
            Option = "test3.txt";
          }else if ( Option.equals("4"))
          { 
                Option = "test4.txt";
          }else
            { 
                System.out.println("You have entered an incorrect selection . . .");
            }
            
            return Option;
        }
        
        //method to choose which test file to use
     private  boolean showContents () throws IOException
     {
        String Option;  
        boolean ans = false;
        BufferedReader reader;  
        reader = new BufferedReader(new InputStreamReader (System.in));  
                                       
         System.out.println("Do you wish to veiw the contents of the array?\n\nEnter 'y' for yes\nEnter 'n' for no\n");  
        
         Option=reader.readLine();  
         if(Option.equals("y"))
         {  
              displayArray();
              ans = true;
         }  else if (Option.equals("n"))
         {
             ans = false;
         }else
         { 
             System.out.println("You have entered an incorrect selection . . .");
         }
            
            return ans;
        }
        
        //method to check if string can be changed to an integer
        private boolean isParsableToInt(String i)
        {
            try
            {
                Integer.parseInt(i);
                return true;
            }
            catch(NumberFormatException nfe)
            {
                return false;
            }
        }
        
        //function to display contents of file that were inputted into array
        private void displayArray()
        {
            for (int i = 0; i < data.length; i++)
            {
                System.out.println(data[i]);
            }
        }
}
    

[Embla Tingeling]

Doubleposted,

http://www.coderanch.com/t/471019/Beginning-Java/java/Global-Array-not-working-please

[Jeff Yan]

because nobody was answering it! sorry, i was getting frustrated with it

[Rob Spoor]

Then you should ask again for an update in the existing thread, but not within 24 hours. As for creating this thread, use one thread per question. Closing this one.