Averaging Grades using Java Swing [closed]

Answer 1

Well , The first mistake than I can see is this :

You are hidden the static array grades in main

int[] grades = new int[50];

Answer 2

You've got the grades array declared twice. Once locally within main(), and the second globally. When you ask for the user to input their grades, you assign the various positions to the array within main(). However, when you get the information in your addTextToPane(), you call on the globally declared grades array.

Once you delete the following in the main(), the problem is resolved.

int[] grades = new int[50];

Answer 3

Decompose the problem, please.

Start with the statistics:

/**
 * Statistics
 * @author Michael
 * @link http://stackoverflow.com/questions/15626262/averaging-grades-using-java-swing?noredirect=1#comment22167503_15626262
 * @since 3/25/13 7:50 PM
 */
public class Statistics {
    public static double getAverage(int numValues, int [] values) {
        double average = 0.0;
        if ((values != null) && (numValues > 0) && (values.length >= numValues)) {
            for (int i = 0; i < numValues; ++i) {
                average += values[i];
            }
            average /= numValues;
        }
        return average;
    }
}

Next I'd recommend that you leave Swing out of it altogether for a little while. Do a text-only input/output UI.

import java.util.Scanner;



/**
 * StatisticsDriver
 * @author Michael
 * @link http://stackoverflow.com/questions/15626262/averaging-grades-using-java-swing?noredirect=1#comment22167503_15626262
 * @since 3/25/13 7:50 PM
 */
public class StatisticsDriver {
    public static final int MAX_VALUES = 50;

    public static void main(String [] args) {
        int [] values = new int[MAX_VALUES];
        Scanner scanner = new Scanner(System.in);
        boolean getAnotherValue;
        int numValues = 0;
        do {
            System.out.print("next value: ");
            String input = scanner.nextLine();
            if (input != null) {
                values[numValues++] = Integer.valueOf(input.trim());
            }
            System.out.print("another? [y/n]: ");
            input = scanner.nextLine();
            getAnotherValue = "y".equalsIgnoreCase(input);
        } while (getAnotherValue);
        System.out.println(Statistics.getAverage(numValues, values));
    }
}

Now that you have those, turn your attention to Swing.

Too many young programmers get themselves wound around the axle on Swing before they solve the problem. Don't make that mistake.