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Thread: Debugging homework assignment/ questions surrounding partially filled arrays

  1. #1
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    Default Debugging homework assignment/ questions surrounding partially filled arrays

    So I'm working on a program that so far

    1) reads a set of numbers from an input file, puts them into an array. The array length is a constant number, but the input file (I run the program twice with different input files) either has more or less then the array size. I'm supposed to count the number of elements in the file including the ones which didnt fit in the array.

    This is my code so far.

    import java.util.Scanner;
    import java.io.*;
     
    public class QudratullahMommandi_3_10
    {
     
       public static void main(String[] args) throws IOException
        {
     
        final String inputFile = "QudratullahMommandi_S_10_Input_Set1.txt";
        final String outputFile = "QudratullahMommandi_S_10_Output_Set1.txt";
        int numOfItems;             // num of items in the array
        final int arrayLength = 15; // setting the array length
        int[] indexHolder;
        double[] valueHolder = new double[arrayLength];  // values from input
     
        // opening input file
        File file = new File(inputFile);    
        Scanner input = new Scanner(file);
     
        // Putting values into the array and getting back the num of items in the array
        // then outputting the num of items
        numOfItems = arraysorter(valueHolder,input);
        System.out.println(numOfItems);
     
     
     
       }
     
     
     
     
       public static int arraysorter(double[]arrayVals, Scanner input) 
        { 
          int subMarker = 0;
          int numOfItems = 0;  
          int arrayLength = arrayVals.length;
          int index = 0;
     
          while (input.hasNext())
          { numOfItems++;
            if  (index < arrayLength)
              { arrayVals[index] = input.nextDouble();
                index++;
              }
           }
     
           return numOfItems;
     
        }// end array Sorter
     
     
     
     
     
     
     
     }// end class

    I'm getting some kind of error where it compiles fine but when I run it, the program never ends. I don't get any output or error messages, it stays running and just never ends... and never outputs anything either.



    This is what my input file I'm using looks like

    88
    80
    66
    99
    22
    88
    54
    100
    77
    29
    100
    98
    66
    11
    73
    98
    100
    7
    21
    Last edited by Helplessdrowningpuppy; April 23rd, 2014 at 12:35 AM.


  2. #2
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    Default Re: Debugging homework assignment/ questions surrounding partially filled arrays

    Most likely you may need to clear the buffer after reading in the double. This is a pretty common issue when using scanners.

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    Helplessdrowningpuppy (April 23rd, 2014)

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    Default Re: Debugging homework assignment/ questions surrounding partially filled arrays

    Quote Originally Posted by Parranoia View Post
    Most likely you may need to clear the buffer after reading in the double. This is a pretty common issue when using scanners.
    I thought it was that but it turned out I had to put something in for the hasNext() clause. I added a trash variable to hold my input for when it didnt fit the if clause and I got it to work.

     
    if  (index < arrayLength)
              { arrayVals[index] = input.nextDouble();
                index++;
              }
     
              else 
              { trashCan = input.nextDouble();
              }

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    Default Re: Debugging homework assignment/ questions surrounding partially filled arrays


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    Helplessdrowningpuppy (April 23rd, 2014)

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    Default Re: Debugging homework assignment/ questions surrounding partially filled arrays

    Quote Originally Posted by Helplessdrowningpuppy View Post
    I thought it was that but it turned out I had to put something in for the hasNext() clause. I added a trash variable to hold my input for when it didnt fit the if clause and I got it to work.
    Using a trash variable is not a good way to implement this unless you are required to store or do something with the excess numbers. Using the trash variable slows down your program needlessly (which is not noticeable in this case, but what if there is a very long list of numbers?), and is not a good habit to get into. Instead, you should add a condition in the while loop to check that the array index is less than the length of the array, e.g.,
    while (input.hasNext() && index < arrayLength)
    This way you can even dispense with the if check in the body of the loop.

    Note that I'm assuming you're not interested in reading all the numbers in the file. If you are, then you can either increase the size of the array, or use a variable-size list such as ArrayList or LinkedList.

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    Helplessdrowningpuppy (April 23rd, 2014)

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    Default Re: Debugging homework assignment/ questions surrounding partially filled arrays

    Quote Originally Posted by jashburn View Post
    Using a trash variable is not a good way to implement this unless you are required to store or do something with the excess numbers. Using the trash variable slows down your program needlessly (which is not noticeable in this case, but what if there is a very long list of numbers?), and is not a good habit to get into. Instead, you should add a condition in the while loop to check that the array index is less than the length of the array, e.g.,
    while (input.hasNext() && index < arrayLength)
    This way you can even dispense with the if check in the body of the loop.

    Note that I'm assuming you're not interested in reading all the numbers in the file. If you are, then you can either increase the size of the array, or use a variable-size list such as ArrayList or LinkedList.
    We run this program twice with different input files, one of length 6 and one of length 19, but we have to use an array size of 15, to get us used to dealing with partially filled arrays. I used the counter because we need to count the number of items which couldnt fit into the array and output the information, if there were extras, srry if I didn't make it clear, I wrote this in a rush but I had weird specs for the program from my professor.

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    Default Re: Debugging homework assignment/ questions surrounding partially filled arrays

    Quote Originally Posted by Helplessdrowningpuppy View Post
    So I'm working on a program that so far

    1) reads a set of numbers from an input file, puts them into an array. The array length is a constant number, but the input file (I run the program twice with different input files) either has more or less then the array size. I'm supposed to count the number of elements in the file including the ones which didnt fit in the array.

    This is my code so far.

     
        int numOfItems;             // num of items in the array
        final int arrayLength = 15; // setting the array length
    Your array length is set to 15, but you have 19 values?

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    Helplessdrowningpuppy (April 23rd, 2014)

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    Default Re: Debugging homework assignment/ questions surrounding partially filled arrays

    Quote Originally Posted by Leklur View Post
    Your array length is set to 15, but you have 19 values?
    Yeah its part of my assignment, we were supposed to read the values from the input file that would fit into the array, and keep a tally of all the values processed so we could output to the console how many values were extraneous if any. So in this case I would output that I had 4 extraneous values.

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