Storing a single csv object into an array

Question

hey ive got a chunk of code thats supposed loads lines of csv file into an array of objects:

public static WarehouseItem[] loadRecords(WarehouseItem[] records) {
  FileInputStream fileStrm = null;
  InputStreamReader rdr;
  BufferedReader bufRdr;
  int numRows = 0;
  String warehouseItem;
  String filename;

  filename = ConsoleInput.readLine("Please enter the filename (DataMillion.csv OR DataThousand.csv)");

  try {
    fileStrm = new FileInputStream(filename);
    rdr = new InputStreamReader(fileStrm);
    bufRdr = new BufferedReader(rdr);

    warehouseItem = bufRdr.readLine();
    records[numRows] = new WarehouseItem(warehouseItem);  //NULL POINTER EXCEPTION HERE
    System.out.println(records[0].toString(records[0].columnVals));
    while (warehouseItem != null) {
      numRows++;
      records[numRows] = new WarehouseItem(warehouseItem);
      warehouseItem = bufRdr.readLine();
    }
  fileStrm.close();
  }

  catch (IOException e) {
    if (fileStrm != null) {
      try { 
    fileStrm.close(); 
      } catch (IOException ex2) {}
    }
    System.out.println("Error in file processing: " + e.getMessage());
    }
    main(null);
    return records;
}

but when i run it, i get a NullPointerException on the line

records[numRows] = new WarehouseItem(warehouseItem);

is there anything that i missed??

heres the WarehouseItem constructor + toString:

public class WarehouseItem {
  String[] columnVals;
  int numColumns = 5;

public WarehouseItem(String warehouseItem) {
  String key, brand, model, price, weightInKG;
  int intWeightInKG;
  double doublePrice; 
  StringTokenizer strTok;

  strTok = new StringTokenizer(warehouseItem, ",");
    key = strTok.nextToken();
    brand = strTok.nextToken();
    model = strTok.nextToken();
    intWeightInKG = Integer.parseInt(strTok.nextToken());
    doublePrice = Double.valueOf(strTok.nextToken());

    weightInKG = String.valueOf(intWeightInKG);
    price = String.valueOf(doublePrice);
  String[] columnVals = {key, brand, model, weightInKG, price};

  if(columnVals.length != 5)
    throw new IllegalStateException("Invalid CSV: not enough columns");
}

public String toString(String[] columnVals) {
  return ("Key:     " + columnVals[0] + "\n" + 
      "Brand:   " + columnVals[1] + "\n" + 
      "Model:   " + columnVals[2] + "\n" + 
      "Weight:  " + columnVals[3] + "\n" + " kg" + 
      "Price:   " + "$" + columnVals[4] + "\n");
}
}

What my problem is the values aren't getting stored into the array records properly and im not sure why

how do i initialize it so that the max number of records is 1000000(1million) — Jad Sapida
– Jad Sapida, Commented Oct 27, 2013 at 14:44

score 2 · Accepted Answer · 2013-10-27 15:36:33Z

2

You didn't initialize array, that was a cause NullPointerException in your code, but if you can't use array don't use it.

The number of lines might exceed the capacity of array, use List instead

List<WarehouseItem> records = new ArrayList<>();

String line = bufRdr.readLine();
while (line != null) {
  WarehauseItem warehauseItem = new WarehauseItem();
  records.add(warehauseItem);
  warehauseItem.processLine(line);
  line = bufRdr.readLine();
}
numRows = records.size();

edited Oct 27, 2013 at 15:36

answered Oct 27, 2013 at 14:51

user2173738

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8 Comments

Kevin Over a year ago

Nope, he's just not creating the individual WarehouseItems.

user2173738 Over a year ago

@Kevin How is not creating if the processLine is called?

Kevin Over a year ago

Trying to call processLine is the NullPointerException.

Kevin Over a year ago

@nikpon Not in yours, the original OP's complaint was the NPE caused by him not initializing the array elements.

Kevin Over a year ago

Yes, it just looks to me like you're implying the error was caused by too many lines. Edit to make it clear the original error was caused by not initializing, and this is just a better approach, then I'll retract my dv.

|

Robin Green · Accepted Answer · 2013-10-27 14:38:01Z

1

When you create an array of objects in Java, it is initialized with all nulls. That is why you get a nullpointerexception.

So you need to create an object for each array position. In fact instead of calling a method you could just make that method a constructor; that would be simpler.

I also noticed another mistake: the method sets local variables, which only exist for the lifetime of the method, when in fact it should set instance variables.

Then I noticed a third mistake: You just caught exception, and assumed that that indicated missing columns; in fact it could indicate invalidly-typed data inside a column (e.g. string instead of integer).

answered Oct 27, 2013 at 14:38

Robin Green

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11 Comments

Jad Sapida Over a year ago

hey thank you for the feedback but what do you mean make the method a constructor? sorry im fairly new

Robin Green Over a year ago

Do you know what a constructor is?

Jad Sapida Over a year ago

yeah just a little familiar with it

Robin Green Over a year ago

I mean you could change processLine into the constructor for the WarehouseItem class.

Robin Green Over a year ago

records[numRows] = new WarehousItem(warehouseItem) instead of records[numRows].processLine(warehouseItem).

|

Prabhakaran Ramaswamy · Accepted Answer · 2013-10-27 15:23:04Z

1

You missed object creation records[numRows]=new WarehouseItem();

Your code need to be like this.

while (warehouseItem != null) {
      records[numRows]=new WarehouseItem();  //here you forgot the object creation.
      warehouseItem = bufRdr.readLine();
      records[numRows].processLine(warehouseItem);
      numRows++; 
 }

edited Oct 27, 2013 at 15:23

answered Oct 27, 2013 at 14:38

Prabhakaran Ramaswamy

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4 Comments

user2173738 Over a year ago

This will produce IndexOutOfBoundsException.

Prabhakaran Ramaswamy Over a year ago

@nikpon yes if the line count is above 1000000 then it will throw IndexOutOfBoundsException

user2173738 Over a year ago

So, your code is unpredictable behavior, you even didn't catch it.

user2173738 Over a year ago

OP catches only IOException, and doesn't care about indexes when using array nor capacity occupied.

Prabhakaran Ramaswamy · Accepted Answer · 2013-10-27 15:25:30Z

1

Because you haven't assigned anything to records[numRows]. You only defined records as an array of WarehouseItem objects. You should assign a new WarehouseItem to that index of the array before you can use.

records[numRows] = new WarehouseItem();
warehouseItem = bufRdr.readLine();
records[numRows].processLine(wareHouseitem);

edited Oct 27, 2013 at 15:25

Prabhakaran Ramaswamy

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answered Oct 27, 2013 at 14:38

regulus

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1 Comment

user2173738 Over a year ago

This will produce IndexOutOfBoundsException.

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