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Hello,

I'm having little trouble solving this question correctly. first of all, I keep failing at testing most of these methods, and I don't know where did i go wrong for them not to work. thus, i'm not able to know if it's solved correctly or not.

Question is:

1.CountNumbers method: computes/returns how many numbers in a file
2.CountNumber method: counts the occurrence a number N is in the file.
3.CountOddNumbers method: to counts how many odd number in the file.
4.sum method: computes/returns the sum/total of numbers in a file
5.average method: computes/returns the average of numbers in a file.
6.sumAboveAverage: to sum the numbers that are greater than the average of all numbers.
7.Standard deviation method: computes/returns the standard deviation of numbers in a file. The standard deviation of N numbers in which their average is μ is calculated as follows:
http://img258.imageshack.us/img258/3231/17445470.png
8.indexOfSmallest: computes/returns the index of the smallest number in the file.
9.indexOfLargest: computes/returns the index of the largest number in the file.
10.copyFile method: to make a duplicate copy of a file (copy (srcFileName, dstFileName).

note: all the methods in the class will operate on a bunch of number (integers/grades) in a file.


and this is what i've done so far
(actually, i've done it all, just need some checking if my methods are logically correct or not).

import java.io.File;
import java.util.Scanner;
import java.io.PrintStream;

public class FileCalculator {

    private static Scanner grades;

    /**
     * @param args the command line arguments
     */
    public static void main(String[] args) throws Exception {
        Scanner sc = new Scanner(new File("grades.in"));
        int res = CountNumbers(sc);
        int res1 = SumMethod(sc);
        // int res2 = CountOddNumbers (sc);
        double resultAverage = AverageMethod(sc);
        System.out.println(res);
        System.out.println(resultAverage);
        copyFile(sc, "copy of grades.out");

    }
/////////////////////////////////////////////////////////////

    public static int CountNumbers(Scanner s) //1
    {
        int count = 0;
        while (s.hasNextInt()) {
            s.nextInt();
            count++;
        }
        return count;
    }
////////////////////////////////////////////////////////////

    public static double countNumber(int[] grades, int numToFind) { //2
        int occurence = 0;
        while (s.hasNextInt()) {
            for (int i = 0; i < grades.length; i++) {
                if (grades[i] == numToFind) {
                    occurence++;
                }
            }
        }
        return occurence;

    }
////////////////////////////////////////////////////////////

    public int CountOddNumbers(int[] grades, Scanner s, Scanner srcFileName) { //3
        int oddCnt = 0;
        while (s.hasNextInt()) {
            for (int i = 0; i < grades.length; i++) {
                if (grades[i] % 2 == 1) {
                    oddCnt++;
                }

            }
        }
        return oddCnt;
    }
////////////////////////////////////////////////////////////

    public static int SumMethod(Scanner s) //4
    {
        int sum = 0;
        while (s.hasNextInt()) {
            sum = sum + s.nextInt();
        }
        return sum;
    }
////////////////////////////////////////////////////////////

    public static double AverageMethod(Scanner s) //5
    {
        double Average = 0;
        int count = 0;
        int sum = 0;
        while (s.hasNextInt()) {
            sum = sum + s.nextInt();
            count++;
        }
        Average = sum / count;
        return Average;
    }
    ////////////////////////////////////////////////////////////

    public static double SumAverageMethod(Scanner s) { //6

        int x = SumMethod(grades);
        double y = AverageMethod(grades);
        double numGreater = 0;
        while (s.hasNextInt()) {
            if (x >= y) {
                numGreater++;
            }
        }
        return numGreater;

////////////////////////////////////////////////////////////    7
    }

    public static double f(double x, double n) {
        return x * x - n;
    }

    public static double df(double x) {
        return 2 * x;
    }

    public static double sqrt(double n) {
        double x = 1;
        for (int i = 0; i < 100; i++) {
            x = x - f(x, n) / df(x);
        }
        return x;


    }

    public static double power(double base, int r) {
        int R = r;
        r = Math.abs(R);
        double res = 1.0;
        for (int i = 0; i < r; i++) {
            res = res * base;
        }
        if (R < 0) {
            return 1.0 / res;
        } else {
            return res;
        }
    }

    public static double f2(double x, int r, double n) {
        return power(x, r) - n;
    }

    public static double df2(double x, int r) {
        return r * power(x, r - 1);
    }

    public static double root(double n, int r) {
        double x = 1;
        for (int i = 0; i < 500; i++) {
            x = x - f2(x, r, n) / df2(x, r);
        }
        return x;
    }

    public static double standardDeviation(Scanner s) {
        double a = CountNumbers(grades);
        double a1 = 1 / a; //       1/n
        double b = SumMethod(grades);
        double getMean = b / a;
        double c = AverageMethod(grades);
        double step1 = 0;
        double step5 = 0;
        while (s.hasNextInt()) {
            a--;
            if (a > 0) {
                step1 = step1 + s.nextInt();// xi is the number s.nextInt() the first number
                double step2 = step1 - c; // xi- averger
                double step3 = sqrt(step2); //(step2)*2
                double step4 = step3 * a1; // 1/n * (step2)
                step5 = root(step4, 1);
                step5 += step5;
                return step5;
            }
        }
        return step5;
    }
//////////////////////////////////////////////////////////// /8

    public static void smallestIndex(double[] grades, Scanner s) {

        double currentValue = grades[0];
        double smallestIndex = 0;
        while (s.hasNextInt()) {
            for (int j = 1; j < grades.length; j++) {
                if (grades[j] < currentValue) {
                    currentValue = grades[j];
                    smallestIndex += j;
                }
            }
        }
    }
//////////////////////////////////////////////////////////// /9

    public static void indexOfLargest(double[] grades, Scanner s) {
        double currentValue = grades[0];
        double largesttIndex = 0;
        while (s.hasNextInt()) {
            for (int j = 1; j < grades.length; j++) {
                if (grades[j] > currentValue) {
                    currentValue = grades[j];
                    largesttIndex += j;
                }

            }
        }
    }
///////////////////////////////////////////////////////////// /10

    public static void copyFile(Scanner srcFileName, String dstFileName) throws Exception {
        PrintStream dst = new PrintStream(new File(dstFileName));
        while (srcFileName.hasNextLine()) {
            dst.println(srcFileName.nextLine());

        }
    }
}
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Last Post by JamesCherrill
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You may have a problem because all these methods read the input file, so after the first method has read it all the subsequent methods will just see end-of-file.
May be better to have a method that reads the file just once into an array then pass that array to each of the methods?

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