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Thread: HELP, I AM HAVING A PROBLEM WITH ADDING VALUES OF AN ARRAY TO A STRING

  1. #1
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    Default HELP, I AM HAVING A PROBLEM WITH ADDING VALUES OF AN ARRAY TO A STRING

    Hi, I seem to be having a consistent error when I try to add the values of an array I created to a String. I keep getting a NullPointerException Error. I went through and checked to make sure that all the values in the array that I am trying to print out are not null. The two arrays are salespersonTotal and productTotal. I don't know what I am doing wrong. Here is my class and tester. Please help if you can. I am pretty new to JAVA and could use all the help I can get.

    Class:
     
    public class Sales
    {
     public Sales()
     {
     }
     
     public Sales(double[][] sales)
     {
      this.sales=sales;
     }
     
     public void salesSlip(int salespersonNumber, int productNumber, double sum)
     {
      sales [salespersonNumber-1][productNumber-1]+=sum;
     }
     public void productTotal()
     {
      int cols=0;
      double sum=0;
      double[] productTotal= new double[sales[0].length];
      for(cols=0; cols<sales[0].length; cols++)
      {
       for(int rows=0; rows<sales.length; rows++)
       {
        sum+= sales[rows][cols];
       }
       productTotal[cols]=sum;
      }
     }
     
     public void salespersonTotal()
     {
      int rows=0;
      double sum=0;
      double[] salespersonTotal= new double[sales.length];
      for(rows=0; rows<sales.length; rows++)
      {
       for(int cols=0; cols<sales[0].length; cols++)
       {
        sum+= sales[rows][cols];
       }
       salespersonTotal[rows]= sum;
      }
      System.out.println(salespersonTotal[0]);
      System.out.println(salespersonTotal[1]);
      System.out.println(salespersonTotal[2]);
     }
     
     public void calcTotal()
     {
      double total=0;
      for(int i=0; i<5; i++)
       total+= 0;
     
     }
     
     public String toString()
     {
      toString="\t\tProduct 1\tProduct 2\tProduct 3\tProduct 4\tProduct 5\tTOTAL\nSalesperson 1";
      for(int i=0; i<sales[0].length; i++)
          toString+="\t"+sales[0][i]+"0";
      toString+="\t"+salespersonTotal[0];
      toString+="\nSalesperson 2";
      for(int i=0; i<sales[0].length; i++)
          toString+="\t"+sales[1][i];
      toString+="\t"+salespersonTotal[1];
      toString+="\nSalesperson 3";
      for(int i=0; i<sales[0].length; i++)
          toString+="\t"+sales[2][i];
      toString+="\t"+salespersonTotal[2];
      toString+="\nTOTAL\t";
      for(int i=0; i<productTotal.length; i++)
          toString+= "\t"+productTotal[i];
      toString+="\t"+total+"0";
     
     
      return toString;
     
     
     }
     
     private double[][] sales;
     private double[] productTotal;
     private double[] salespersonTotal;
     private String toString;
     private double total;
     
    }

    Tester:

     
    public class SalesTester
    {
     public static void main(String[] args)
     {
      double[][] sales={{0.00,0.00,0.00,0.00,0.00},{0.00,0.00,0.00,0.00,0.00},{0.00,0.00,0.00,0.00,0.00}} ;
      Sales tester= new Sales(sales);
     
      tester.salesSlip(1,1,20.00);
      tester.salesSlip(1,2,30.00);
      tester.salesSlip(1,3,0.00);
      tester.salesSlip(1,4,10.00);
      tester.salesSlip(1,5,0.00);
      tester.salesSlip(2,1,0.00);
      tester.salesSlip(2,2,0.00);
      tester.salesSlip(2,3,10.00);
      tester.salesSlip(2,4,0.00);
      tester.salesSlip(2,5,30.00);
      tester.salesSlip(3,1,50.00);
      tester.salesSlip(3,2,60.00);
      tester.salesSlip(3,3,50.00);
      tester.salesSlip(3,4,30.00);
      tester.salesSlip(3,5,35.00);
     
      tester.productTotal();
      tester.salespersonTotal();
      tester.calcTotal();
      System.out.println(tester.toString());
     }
    }

    This is my output and error:

    60.0
    100.0
    325.0
    java.lang.NullPointerException
    at Sales.toString(Sales.java:62)
    at SalesTester.main(SalesTester.java:27)
    at sun.reflect.NativeMethodAccessorImpl.invoke0(Nativ e Method)
    at sun.reflect.NativeMethodAccessorImpl.invoke(Native MethodAccessorImpl.java:39)
    at sun.reflect.DelegatingMethodAccessorImpl.invoke(De legatingMethodAccessorImpl.java:25)
    at java.lang.reflect.Method.invoke(Method.java:597)
    at edu.rice.cs.drjava.model.compiler.JavacCompiler.ru nCommand(JavacCompiler.java:271)
    >

    The three numbers are the values in the array. Can you all take a look.


  2. #2
    Super Moderator Norm's Avatar
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    Default Re: HELP, I AM HAVING A PROBLEM WITH ADDING VALUES OF AN ARRAY TO A STRING

    java.lang.NullPointerException
    at Sales.toString(Sales.java:62)
    What variable at line 62 is null? Then backtrack in your code to findout why it does NOT have a valid value.
    If you can not tell by looking add a println statement just before line 62 to print out the value of ALL the variables used in line 62.

  3. #3
    Super Moderator Norm's Avatar
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    Default Re: HELP, I AM HAVING A PROBLEM WITH ADDING VALUES OF AN ARRAY TO A STRING

    Is this a duplicate posting of the same problem?
    NullPointerException Error

  4. #4
    Super Moderator copeg's Avatar
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    Default Re: HELP, I AM HAVING A PROBLEM WITH ADDING VALUES OF AN ARRAY TO A STRING

    Do not post duplicate questions to the forums. I am locking this thread.

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