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Thread: Creating a program that reads from a file

  1. #1
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    Default Creating a program that reads from a file

    Im working on a problem today and I getting errors for some reason.

    Problem statement:
     
    Design and implement an application that creates a histogram,
    which allows you to visually inspect the frequency distribution
    of a set of values.  The program should read in an arbitrary
    number of integers that are in the range 1 to 100 inclusive;
    then produce a chart similar to the one below that indicates
    how many input values fell in the range 1-10, 11-20, and so on.
    Print one asterisk for each value entered.

    Here's the catch, making that problem is okay for me, but what if i wanted it to create it from reading values from a txt file?

    This is my final code:

     
    import java.util.*;
    import java.io.*;
     
     
    public class Histogram 
    {
     
     
    	public void displayIntArray(int[] iAr)
    	{
    		for(int index = 0; index < iAr.length; index++)	
    		{
    			System.out.println(iAr[index]);
    		}
    	}
     
     
    	public int[] readIntArrayFromFile(String fileName) throws Exception
    	{
    		Scanner fileScan  = new Scanner(new File(fileName));
    		int counter = 0;
    		while(fileScan.hasNext())
    		{
    			fileScan.next();
    			counter++;
     
    		}
     
    		int[] iArray = new int[counter];
     
    		Scanner fScan  = new Scanner(new File(fileName));
    		counter = 0;
    		while(fScan.hasNext())
    		{
    			iArray[counter] = fScan.nextInt();
    			counter++;
    		}
     
    		return iArray;
     
     
     
     
     
    	}
     
    	public int[] initializeCounterArray(int[] inArray) 
    	{
    		final int SIZE = 10;
    		final int MIN = 1;
    		final int MAX = 100;
    		int[] counters = new int[SIZE];
    		int n, nextt, ix;
     
     
    		while (n < 0);
    		{
    		  int[] numbers = new int[n];
    		}
     
     
    		for (int index = 0; index < inArray.length; index++) 
    		{
    			int number = inArray[index];
    			if (number >= MIN && number <= MAX) {
    				int newIndex = (number - 1) / SIZE;
    				counters[newIndex]++;
    			}
     
    		}
     
    		return counters;
     
     
     
      // Creates the histogram values
     
      String[] stars = {" 1 - 10 |", "11 - 20 | ", "21 - 30 | ", "31 - 40 | ", "41 - 50 | ",
                     "51 - 60 | ", "61 - 70 | ", "71 - 80 | ", "81 - 90 | ", "91 - 100 | "};
     
      //10 strings for the different parameters
     
      for (ix = 0; ix < n; ix++) 
      {
          nextt = numbers[ix];
     
          if (nextt < 11) 
          {
              stars[0] += "*";
          } 
          else
          {
            if (nextt < 21) 
            {
              stars[1] += "*";
          } 
     
            else
            {
              if (nextt < 31) 
          {
              stars[2] += "*";
          }
          else
          {
            if (nextt < 41) 
          {
              stars[3] += "*";
          }
          else
          {
            if (nextt < 51) 
          {
              stars[4] += "*";
          } 
          else
          {
            if (nextt < 61) 
          {
              stars[5] += "*";
          } 
          else
          {
            if (nextt < 71) 
          {
              stars[6] += "*";
          } 
          else
          {
            if (nextt < 81) 
          {
              stars[7] += "*";
          } 
          else
          {
            if (nextt < 91) 
          {
              stars[8] += "*";
          } 
          else 
          {
              stars[9] += "*";
          }
      }
      for (ix = 0; ix < 10; ix++) {
          System.out.println(stars[ix]);
      }
     
    }
          }
     
          }
          }
          }
            }
          }
      }
    	}
    }

    I've got the driver class all good to go but just in case:
     
    public class Driver 
    {
    	public static void main(String[] args) throws Exception
    	{
    		int[] numbers, counters;
    		Histogram hist = new Histogram();
     
    		numbers = hist.readIntArrayFromFile("data-8.3.txt");
    		counters = hist.initializeCounterArray(numbers);
     
    		hist.displayIntArray(counters);
    	}
     
    }

    The only error im getting from this is the " nextt = numbers[ix]; " part of the code. ive tried implementing some commands at the top but nothing worked. But does everything look good? So if you feel that the code is not good, please feel free to make any required changes.

    I appreciate everyone taking their time out of their day to help me out, it really means alot

    Thank you!


  2. #2
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    Default Re: Creating a program that reads from a file

    Please copy and paste here the full text of the error messages you are getting.

  3. #3
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    Default Re: Creating a program that reads from a file

     
    Exception in thread "main" java.lang.Error: Unresolved compilation problem: 
    	numbers cannot be resolved to a variable
     
    	at Histogram.initializeCounterArray(Histogram.java:85)
    	at Driver.main(Driver.java:10)

  4. #4
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    Default Re: Creating a program that reads from a file

    On line 85 of the Histogram class you are attempting to use the numbers variable which has either not been declared or it has been declared in the wrong scope.

    By the way what is the purpose of the following code? Maybe I should rephrase the question, what exactly is this code doing not what do you think it should be doing?
    while (n < 0);
    {
        int[] numbers = new int[n];
    }
    Improving the world one idiot at a time!

  5. #5
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    Default Re: Creating a program that reads from a file

    Im trying to create a histogram which reads values from a txt file and then displays how many of each corresponds in each interval.

    For:
     
    while (n < 0);
    {
        int[] numbers = new int[n];
    }

    How could i resolve this issue? could i just declare numbers a brand new int[]?

    Thanks!

  6. #6
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    Default Re: Creating a program that reads from a file

    Take a close look at that code. Problems are:
    1. You have placed a semi-colon after the while statement which makes the rest of the code outside the loop.
    If you fix that
    2. You have declared the array inside the loop and therefore it cannot be used outside the loop.
    3. You create a new array each time around the loop which means the previous array is thrown away. What possible reason would you need to do that?
    4. The value of n never changes therefore it might be an infinite loop or might never enter the loop depending upon the value of n.
    5. For the loop to enter the value of n must be negative. Inside the loop you make an array with a length of n. It is impossible to make an array with a negative length.
    Improving the world one idiot at a time!

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