Storing variables in array?

Question

I need to find the deviation of multiple homework values. In order to do this, i need to store a variable homework, that is in a for loop, so it deletes itself every time it executes. Also, the number of variables i need in order to store the seperate homework score values is unknown, so i can't just make a list of variables. I think what i need to do is do a list of arrays, but im not sure if im doing it right.

here is the code of the method that includes the array i have created...

 public double computeHomeworkDeviation(int homework){
    int[] homeworkScore = new int[totalStudents];
    if(computeHomeworkDeviationCounter < totalStudents){
        homeworkScore[computeHomeworkDeviationCounter] = homework;
        computeHomeworkDeviationCounter++;
    }
    else{
        for(int k = 1; k <= totalStudents; k++){
            top += Math.pow(homeworkScore[totalStudents - k] -    homeworkAverage, 2);
        }
    homeworkDeviation = Math.sqrt(top / totalStudents); 
    }
    return homeworkDeviation;
}

this method is called to a for loop and calls the argument of the homework variable that needs to be stored in an array list. What i have isn't working, what am i doing wrong? (i don't believe the array values are even being stored)

edit: I now split it into 2 methods.

setArrayMethod...

 public void setHomeworkArray(int homework){
    homeworkScore[l] = homework;
    l++;
}

computeHomeworkDeviationMethod...

 public double computeHomeworkDeviation(int homework){
        for(int k = 1; k <= totalStudents; k++){
            top += Math.pow(homeworkScore[totalStudents - k] -          homeworkAverage, 2);
        }
    homeworkDeviation = Math.sqrt(top / totalStudents); 
    return homeworkDeviation;
    }

am getting ArrayOutOfBoundsException error still.

What i have isn't working, Not working in which sense. error? wrong output? what — Prateek
– Prateek, Commented Nov 1, 2013 at 23:25
I am getting the wrong value for homeworkDeviation and i believe it has something to do with storing the homework values in the array. — Jacob Stinson
– Jacob Stinson, Commented Nov 1, 2013 at 23:26
move int[] homeworkScore = new int[totalStudents]; outside the function — Iłya Bursov
– Iłya Bursov, Commented Nov 1, 2013 at 23:27
There is only one array assignment in your code. Your for loop does not assign anything — newtonrd
– newtonrd, Commented Nov 1, 2013 at 23:29

kviiri · Accepted Answer · 2013-11-01 23:28:32Z

1

Your hunch is correct, the values aren't storing properly. I'm not sure what exactly you want your program to do but I think you'd want a loop instead of if when storing values in the array:

while(computeHomeworkDeviationCounter < totalStudents){
    homeworkScore[computeHomeworkDeviationCounter] = homework;
    computeHomeworkDeviationCounter++;
}

This also means you'll have to remove the else statement. Finally, to avoid errors if this method is executed several times, I recommend resetting the variables computeHomeworkDeviationCounter when the method is called:

public double computeHomeworkDeviation(int homework){
int[] homeworkScore = new int[totalStudents];
computeHomeworkDeviationCounter = 0;

...or even having it as a method-local variable if it isn't used anywhere else:

public double computeHomeworkDeviation(int homework){
int[] homeworkScore = new int[totalStudents];
int computeHomeworkDeviationCounter = 0;

And likewise for the variable top if appropriate for the rest of your program.

answered Nov 1, 2013 at 23:28

kviiri

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1 Comment

Jacob Stinson Over a year ago

i edited my submission...also, the values do not need to be reset in the code.

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