Methods and Arrays Help

[Karen Wen]

Hi, I've been stuck and completely lost on my Java class program since yesterday and I cannot seem to figure out how to resolve these issues since these are just the beginning parts of the program. Can someone guide/hint to me what I need? I will be putting up the parts where I'm stuck at and giving some general information.

I have two classes, SalesStats and Divisions.

In SalesStats class, I have a main that creates a Division object. I'm not sure what the arrays are suppose to be.

   public class SalesStats
{
   public static void main(String[] args) throws IOException
   {
	  Divisions[][] d = new Divisions[div.setSales][]; //stuck here
   }

I am to read a file and store the data into two dimensional arrays with a method called readValues(Divisions d). This method is to store the file into array d.
The file input is like this:
1234
2345
3456
4567
12345
23456
34567
45678
etc...

I need to set this up so that the arrays will read as 6 rows (divisions) and 4 columns (quarters).

Output will be:
Division1:
1234
2345
3456
4567
Division2:
12345
23456
34567
45678
etc..

Here is the method I'm stuck at:

   public String readValues(Divisions d)
   {
	  int num = 0;
	  Scanner keyboard = new Scanner(System.in);
      System.out.print("Please enter input filename: ");
      String input = keyboard.nextLine();

      File myfile = new File(input);
      if (!myfile.exists())
      {
         System.out.println("input file " + input + " does not exist");
         System.exit(0);
      }
      Scanner inputFile = new Scanner(myfile);
      while (inputFile.hasNext())
      {
         for (int i = 0; i < d.DIVISION; i++)
            for(int j = 0; j < d.QUARTERS; j++)
            	[i][j] = div.setSales; // I'm stuck here on how to store the input into the array d
      }
      inputFile.close();
   }
}
  

In Divisions class I'm having trouble with setting div and qrt.

  public class Divisions
{
   public final int DIVISION = 6;
   public final int QUARTERS = 4;
   private double[][] sales;
   public void setSales(int div, int qrt, double amount)
   {
      DIVISION = div; //error
      QUARTERS  = qrt; //error
      amount = sales[DIVISION][QUARTERS]; // I'm guessing sales means amount, but I am not sure
   }  

Sorry if this is confusing, I will try to clear the problem more if there's a question.
Thank you!

[Steve Luke]

Start with the setSales method:

   public final int DIVISION = 6;
   public final int QUARTERS = 4;
...
      DIVISION = div; //error
      QUARTERS  = qrt; //error

What does final mean?

[Campbell Ritchie]

. . . and welcome to the Ranch

[Karen Wen]

Hi and thank you! I have resolved my issues above, but now when I execute, I get a NullPointerException. Can someone guide me to what I need to do?

  Exception in thread "main" java.lang.NullPointerException
        at Divisions.setSales(Divisions.java:8)
        at SalesStats.readValues(SalesStats.java:33)
        at SalesStats.main(SalesStats.java:9)  

Codes in Divisions:

  public class Divisions
{
   public final int DIVISION = 6;
   public final int QUARTERS = 4;
   private static double[][] sales;
   public static void setSales(int div, int qrt, double amount)
   {
      amount = sales[div][qrt]; //problem here
   }  
}

Codes in SalesStats:

  public class SalesStats
{
   public static void main(String args[]) throws IOException
   {
      Divisions d = new Divisions();
      readValues(d); //problem here
      ...
    }
}
   public static void readValues(Divisions d) throws IOException
   {
      ...
      for (int i = 0; i < d.DIVISION; i++)
         for (int j = 0; j < d.QUARTERS; j++)
         {
            Divisions.setSales(i,j,inputFile.nextDouble()); //problem here
         }
   }
}
   

[Gary Ba]

Did you allocate and assign anything for sales?

  
 public class Divisions  
{  
    public final int DIVISION = 6;  
    public final int QUARTERS = 4;  
    private static double[][] sales;  
    public static void setSales(int div, int qrt, double amount)  
    {  
       amount = sales[div][qrt]; //problem here  
    }    
 } 
 

[Karen Wen]

Gary Ba wrote:Did you allocate and assign anything for sales?

  
 public class Divisions  
{  
    public final int DIVISION = 6;  
    public final int QUARTERS = 4;  
    private static double[][] sales;  
    public static void setSales(int div, int qrt, double amount)  
    {  
       amount = sales[div][qrt]; //problem here  
    }    
 } 
 

I don't think I did. Am I suppose to? How/where do I put it? I'm suppose to import a text file that stores the text into arrays as said on my first post.

Edit:
Ok, I've initially assigned sales. When executed, it's all 0.0 and not the numbers I need. Here are parts of the program. What am I doing wrong?

  public class Divisions
{
   public final int DIVISION = 6;
   public final int QUARTERS = 4;
   private static double[][] sales;
   public static void setSales(int div, int qrt, double amount)
   {
      double[][] sales = new double[6][4];
      amount = sales[div][qrt];
   }
   public static double getSales(int div, int qrt)
   {
      double[][] sales = new double[6][4];
      return sales[div][qrt];
   }  

     public static void readValues(Divisions d) throws IOException
   {
      Scanner keyboard = new Scanner(System.in);
      System.out.print("Please enter input filename: ");
      String input = keyboard.nextLine();

      File myfile = new File(input);
      if (!myfile.exists())
      {
         System.out.println("input file " + input + " does not exist");
         System.exit(0);
      }
      Scanner inputFile = new Scanner(myfile);
      for (int i = 0; i < d.DIVISION; i++)
         for (int j = 0; j < d.QUARTERS; j++)
         {
            Divisions.setSales(i,j,inputFile.nextDouble());
         }
      inputFile.close();
   }
   public static void displaySales(Divisions d)
   {
      System.out.println("SALES AMOUNT BY DIVISION");
      System.out.println("========================");
      for (int i = 0; i < d.DIVISION; i++)
      {
         System.out.println("DIVISION " + (i+1));
         for (int j = 0; j < d.QUARTERS; j++)
         {
            System.out.println("Quarter " + (j+1) + " : ");
            System.out.println(Divisions.getSales(i,j));
         }
      }
   }  

[Campbell Ritchie]

You appear to be assigning amount to what is in sales for a particular square. Since you haven't done anything with sales yet, that will be 0. I suspect you want your assignment the other way round.

[Campbell Ritchie]

If you have final ints, declare sales as new double[DIVISIONS][QUARTERS] rather than using 6 and 4. If you have the numbers, you might as well use them, and that style reduces the risk of errors like entering 5 by mistake.
Also, since you are assigning sales in the setSales method, you will create a new array every time you run that method and lose all you old information. Similarly for your getSales method. You want to create sales in a constructor, I think.