Methods and Arrays with file input- I'm so lost!

[T Johnson]

Alright, so this is the last assignment for my class and I'm so completly lost it's not even funny.

I've tried looking up youtube videos and reading from the book but I just don't understand what I'm doing.

So basically he gave us a half written program and he's asking us for the following:

getArrayFile, getArrayMean, getArrayStdDev, assignGrade, getArrayGrades, getMaxScore, getMinScore, and lastly DisplayGrades...



txt file contains:

96, 78, 76, 65, 91, 42, 89, 83, 77, 83, 93, 54, 61, 84, 79, 39, 92, 72, 74, 82, 64, 65, 92, 72, 74, 82, 64, 65, 92, 45, 37, 69, 72, 91, 64

Program is as followed

package hw8;

import java.util.Scanner; // Scanner is in java.util
import java.io.* ;

public class GradeScores {

    final static int LIMIT = 100;
    static boolean debug = true; // to debug
    // set it to true if want to debug, set it to false at the end

    /** Main method */
    public static void main(String[] args) throws IOException
    {
    int dataCount, maxNumOfScores, maxScore = -1, minScore = -1;
    String inpFileName, outFileName;
    double dataAvg = 0, dataStdDev = 1;

    if (debug)
        System.out.println("args.length=" + args.length); // to test

    // process the command line arguments
    if (args.length < 2)
    {
        System.err.println("Error. Must have at least two arguments. Execution: ");
        System.err.println("java p8partial " +
                  "<inputFile> <outputFile> [<MaxNumerOFScores>]");
        System.exit(1);
    }
 
    // file names are coming from teh command line arguments
    inpFileName = new String(args[0]); // 1st cmd.line arg. to the main
    outFileName = new String(args[1]); // 2nd cmd.line arg. to the main
   
    if (args.length == 2)
        maxNumOfScores = LIMIT;  // default, if not given in C.L.Arg list
    else
        maxNumOfScores = Integer.parseInt(args[2]); // 3nd cmd.line arg. to the main

    // can declare arrays now
    int[] examScores = new int[maxNumOfScores];   // scores array declaration
    char[] examGrades = new char[maxNumOfScores]; // grades array declaration
   
    // initilaize grades
    for (int i = 0; i < maxNumOfScores; i++)
        examGrades[i] = 'x';

    // create a Scanner object from input data file
    File inpf = new File (inpFileName);
    Scanner input = new Scanner(inpf);

    // create a PrintWriter object from output data file
    File outf = new File(outFileName);
    PrintWriter output = new PrintWriter(outf);

    // get the input
    dataCount = getArrayFile(input,  examScores);

    // to test data reading
    printArray(examScores, dataCount, "input values");

    // NEED TO COMPLETE THE REST


    // display scores and grades at the end
    displayGrades(output, examScores, examGrades, dataCount, dataAvg, dataStdDev, maxScore, minScore);
   
   
    output.close();
    input.close();
   
    } // end-main
   

    public static int getArrayFile(Scanner s, int[] arr)
    //////////////////////////////////////////////////////////////////
    // s, arr are the formal arguments.                              //
    // Scanner s is assumed to be set by the caller (i.e., main)     //
    // by opening up a File.                                         //
    // arr elements are read from s until the End-of-File is reached.//
    // This update to arr elements are permanent.                    //
    // (i.e., passed by reference).                                  //
    // The number of data entered is returned to the caller which    //
    // is the logical size of the array arr.                         //
    ///////////////////////////////////////////////////////////////////
    {
    int count;
 
    count = 0;
    while (s.hasNext() && (count < arr.length))
    {
        arr[count] = s.nextInt();
        count++;
    }
   
    return count;
    } // end-getArrayFile

    public static void printArray(int[] arr, int numOfElems, String msg)
    // arr and numOfElems are the formal arguments.
    // arr is passed by reference and but its elements are not set
    // (NOT modified) by the function.
    // numOfElems is passed bay value.
    // assume that the array arr has numOfElems elements.
    // This method will print numOfElements and the values in the array arr.
    {
    System.out.println("The array " + msg + " has " + numOfElems + " elements.");
    System.out.println("Values in array:");

    for (int i = 0; i < numOfElems; i++)
        System.out.print(arr[i] + ", ");

    System.out.println();

    } // end-printArray

    public static void displayDashedLine(PrintWriter out, int len)
    // to display a line of dashes '-'
    // assumes the PrintWriter out is set.
    {
        for (int i = 0; i < len; ++i)
            out.print("-");
        out.println();
    } // end-displayLine

    public static void displayGrades(PrintWriter outFile, int[] scores, char[] grades, int count,
                     double avg, double stddev, int max, int min)
    // to display scores and grades together with avg. and stddev
    // assumes the PrintWriter outFile is set.
    {
        outFile.printf("\nCount=%3d, avg=%6.2f, stddev=%6.2f, max=%3d, min=%3d\n",
               count, avg, stddev, max, min);
        outFile.println("\n id\tscore\tgrade");
        displayDashedLine(outFile, 25);
        for (int k = 0; k < count; ++k)
            outFile.printf("%3d\t%3d\t%c\n", k+1, scores[k], grades[k]);

        displayDashedLine(outFile, 25);
    outFile.println();
    } // end-displayGrades
   
    // NEED TO ADD OTHER METHODS HERE

} // end-class

any helps or suggestions would be greatly appreciated.

[Tushar Goel]

So what is your question? Where did you stuck? What have you done so far ?

[Stefan Evans]

It looks pretty good to me.
What I would expect to see next is something like:

// in your main logic somewhere: 
maxScore = findMaxScore(grades);


	/**Finds the highest score in the list of scores given
	 * @param scores array of scores
	 * @return Maximum score of the scores provided. 
	 */
	public int findMaxScore(int[] scores){
              // provide a better implementation of find max score here
		return 0;
	}

[Liutauras Vilda]

T Johnson,

Just so you know, your code indentation is quite poor: lots of missing curly braces, formatting also inconsistent.

[Campbell Ritchie]

I would also say your main method is much too long. It should look something like this:-

public class GradeScoreDemo
{
   public static void main(String[] args)
   {
      new GradeScoreDemo().run();
   }

   private GradeScoreDemo()
   {
   }

   private void run()
   {
      GradeScores gs = new GradeScores("myFile.txt");
      gs.getArrayFile());
      System.out.println(gs.getArrayMean());
      System.out.println(gs.getArrayStdDev());
      gs.assignGrade();
      gs.getArrayGrades();
      System.out.println(gs.getMaxScore());
      System.out.println(gs.getMinScore());
      gs.DisplayGrades();
   }
}

Actually you should have an entire class which looks like that. You can consider creating two GradeScore instances (particularly if you have two files) and you may need to put the method calls in a different order. And you will need to do something more with the print calls.

Now you should find that corresponds to the grades scores class so you can call all the methods in turn.

And welcome to the Ranch

[Campbell Ritchie]

If you want to count command‑line arguments then this is the correct usage:-

// ...
public static void main(String[] args)
{
   if (args.length > 1)
   {
      new XYZ(args[0], args[1]).run(); // or similar
   }
   else
   {
      System.err.printf("Two command-line arguments required:%n" +
          "File name and number of grades to count:%n" +
          "Usage: java GradeScoreDemo C\\MyDocuments\\MyFile.text 20%n");
   }
}

Since you are supposed to be writing object‑oriented programming, expunge the word static from your vocabulary (except for the main method).