努力将数组值传递给方法

Question

i'm struggling a bit with getting array values from one method into another without repeating the method over again (the method obtains judges scores using getScannerInput (we have to use it at my uni instead of other options :-/ ).

My program is the following;

public class mark4

{

static int SIZE = 10; // Define array size
static int classMarks[] = new int [SIZE]; // Initialise array classMarks[]
static double max = 0; 
static double min = 0;
static double total = 0;
static double averagescore = 0;
static int pass = 0;

 public static int[] getMarks()
{
    int[] classMarks = new int [SIZE];

    for(int i = 0; i< classMarks.length; i++) // Start input loop to obtain marks
    {
        classMarks[i] = getScannerInput.anInt("Please enter students mark: ");
    }


        System.out.print("\nThe marks for this class are; "); // Output initial line to be completed with students marks

    for(int i=0; i<classMarks.length; i++) // Start output loop to output students marks
    {
        System.out.print(classMarks[i] + ", "); // Output marks separated by a comma and a space

    }

    return classMarks;
}

public static double averagescore(){

    for(int i=0; i<classMarks.length; i++) // Start loop to calculate total of all marks.
    {
        total = classMarks[i] + total; // Calculate total of array by traversing and adding to 'total' variable each time
        averagescore = total / classMarks.length; // Divide array total by array length to find average

    } // end average loop

        return averagescore;    

}

public static double min(){

    min = classMarks[0]; // Set min to first value of array to compare to rest


    for(int i=0; i<classMarks.length; i++) // Start loop to calculate minimum and maximum scores
    {
            if(classMarks[i] < min) // Compare values on each iteration, if value is less than current 'min' value, replace min with new value
                    min = classMarks[i];

    } // end minloop

    return min;
}

public static double max(){

    max = classMarks[0]; // Set max to first value of array to compare to rest


    for(int i=0; i<classMarks.length; i++) // Start loop to calculate minimum and maximum scores
    {
        if(classMarks[i]>max) // Compare values on each iteration, if value is greater than current 'max' value, repalce max with new value
                    max = classMarks[i];

    } // end max loop

    return max;
}

public static int pass(){

    for(int i=0; i<classMarks.length; i++) // Start loop to calculate how many students passed with a mark of 8 or higher
    {
            if( classMarks[i] >= 8 ) // Compare the current score in each iteration to 8 to see if it is more than or equal to the pass mark

                    pass++; // If current value is greater than or equal to pass mark, add one to pass counter.

    } // end pass loop

    return pass;
}

public static void main (String args[])
{

    int[] classMarks = getMarks();
    double averagescore = averagescore();
    double min = min();
    double max = max();
    int pass = pass();

                System.out.print("\nThe number of students who passed the exam is " + pass);
                System.out.printf("\nThe class average correct to 1 decimal place is: %4.1f", averagescore); // Output average score to 1 decimal place
                System.out.printf("\nThe lowest mark obtained in this class was: %3.1f", min); // Output lowest score to one decimal place (in case of half marks...)
                System.out.printf("\nThe highest mark obtained in this class was: %3.1f", max); // Output highest score to one decimal place (in case of half marks...)


} // end main

} // end class

The program compiles correctly, but the results I get are all 0 or 0.0, suggesting that the methods aren't taking the figures input during the getScores() method.

If I try to define the results for classMarks[] inside the methods using;

int[] classMarks = getMarks();

it repeats the whole getScores() method and asks for the results again every time it encounters a method in the main.

I'm aware this is probably a fairly simple answer, but we had to do this as a question in an assessment, but i missed the lectures on methods and arrays and i'm struggling a bit with some minor elements.

Any help would be much appreciated!

Answer 1

You declare this, which I beleive is what you intend to use,

static int classMarks[] = new int [SIZE];

but, within getMarks(), you declare a new one:

int[] classMarks = new int [SIZE];

which is what will be used within the scope of that method.

Either, you should use the class scope variable, and not declare others which will override it (that is, remove the second declaration shown above), or your min, max, etc. methods should take the an int[] argument, and you could pass the array returned from getMarks() to them.

Answer 2

In your main method you are declaring classMarks, which is hiding the static classMarks you have at the class level. You are also declaring another classMarks array within your getMarks method, so your scanner is never reading into the shared classMarks array, only into the local array in getMarks, which is then returned and placed in the local classMarks variable in main, but never getting into your static variable that is referenced by every other method in the class.