Java scanner as part of another method

Question

I am working on a lab for one of my classes, so I am looking for more explanation than for the actual code.

For part of this assignment, I need to read numbers from the user until the -d command is pressed. I have a while loop in a method and I pass the scanner to this method, here is my main method:

    Scanner scan = new Scanner(System.in);

    System.out.println("Length:");
    int length = 0;

    if(scan.hasNextInt()){
        length = scan.nextInt();
    }

    if(length<0 || length>100){
        System.out.println("Length is not of the proper size");
        scan.close();
        return;
    }

    Double[] a1 = new Double[length];
    Double[] a2 = new Double[length];
    fillWithZeros(a1);
    fillWithZeros(a2);

    System.out.println("Enter the numbers to be multiplied:");

    a1 = fillWithValues(a1,scan);
    a2 = fillWithValues(a2,scan);
    double total = calculateTotal(a1,a2);
    printVector(a1,"a1");
    printVector(a2,"a2");
    System.out.println("Total: " + total);
    scan.close();

Then here is my fillWithValues ​​method:

public static Double[] fillWithValues(Double[] array, Scanner scan) {
    int numberOfElements = 0;
    while(scan.hasNextDouble()){
        if(numberOfElements<array.length){
            array[numberOfElements] = scan.nextDouble();
            numberOfElements++;
        }else{
            return array;
        }
    }
    return array;
}

The problem I am facing is that when I press Control-D, it does not end the input stream as it should, but I have the code above, it will end the input stream, so can someone explain why Am I having this problem?

I would just declare the scanner as a global variable, but I am not allowed to use global variables for this purpose.

Answer 1

a1 = fillWithValues(a1,scan);
a2 = fillWithValues(a2,scan);

fillWithValues()

while(scan.hasNextDouble()){
   ...
}

, EOF (CTRL-D Unix), scan.hasNextDouble() false, , , ( CTRL-D, ).

, ( ) .

, boolean ( , , ):

public static boolean fillWithValues(Double[] array, Scanner scan) {
    int numberOfElements = 0;
    while(scan.hasNextDouble()){
        if(numberOfElements<array.length){
            array[numberOfElements] = scan.nextDouble();
            numberOfElements++;
        }else{
            return true;  // all elements read
        }
    }
    return false;   // input aborted
}

, :

if (fillWithValues(a1,scan) == true) {
    fillWithValues(a2,scan);  // could also check the return value again if required
}

BTW, static , - . , static, .

Answer 2

hasNextDouble(), :

true, nextDouble(). - .

, Ctrl-D , , enter. , fillWithValues() , hasNextDouble() false ( Ctrl-D). -, - , fillWithValues() , . , ( Ctrl-D, ).