How do i initialize array of a another class?

Question

I am trying to initialize an array based on user input so it can be of any custom size. By default i have initialized array to 10 with all 0.0 values but when I try call the method that initializes the array nothing happens and the values neither the size or the values in the array change.

Class Numbers:

public class Numbers {
private Float [] numbers;
private int default_size = 10;

public Numbers() {
    ///  write code here to intialize a "default" array since this is the default constructor
    numbers = new Float[default_size];
    for(int i = 0; i < default_size; i++)
    numbers [i] = (float) 0.0;
}

public Numbers (int size) {
    ///  write code here to initialize an "initial" array given the parameter size as this is an initial constructor
    numbers = new Float[size];
}

public void initValuesInArray() {
    /// write code here to intialize the values in the array
    Scanner scan = new Scanner(System.in);
    for (int i = 0; i < numbers.length; i++) {
        System.out.println("Enter Value : ");
        numbers[i] = scan.nextFloat();
    }
}

public String toString() {
    // write code to return the values in the array in a list format - one value per line
    for (int i = 0; i < numbers.length; i++)
    System.out.println(numbers[i]);
    return " ";
}

public float calcAverage() {
    // write code to return the average of the values in the array
    double sum = 0.0;
    for (int i = 0; i < numbers.length; i++)
        sum += numbers[i];
    double average = sum / numbers.length;
    System.out.println(average);
    return (float) average;
}

}

Class Main:

public class Main {
public static void main (String [] args) {

    // write the code here to implement the menu as specified in Lab 1

    boolean menuLoop = true;
    while(true) {
    System.out.println("Enter 1 to initialize a default array");
    System.out.println("Enter 2 to initialize an array of input size");
    System.out.println("Enter 3 fill array with values");
    System.out.println("Enter 4 display values in array");
    System.out.println("Enter 5 to display average of the values in the array");
    System.out.println("6 to quit\n");

    Numbers obj = new Numbers();
    Scanner scan = new Scanner(System.in);
    int i = scan.nextInt();

    switch (i) {

    case 1:
        obj = new Numbers ();
        break;

    case 2:
        System.out.println("Enter the new size of array: ");
        int x = scan.nextInt();
        Numbers [] numbers = new Numbers[x];
        break;

    case 3:
        System.out.println("Enter the float numbers as values in the array: ");
        obj.initValuesInArray();
        break;

    case 4:
        obj.toString();
        break;

    case 5:
        obj.calcAverage();
        break;

    case 6:
        System.exit(0);
        break;
    default :
        System.out.println("Invalid Entry...");
        break;
        }

    } 
}

}

It needs to be able to change the size of the array based on user input and thereafter the user can enter the values into the array.

EDIT:

I think i have finally figured out the issue here and that is when i use break in the switch statement it initializes the array to default which is 10 with all 0.0 values. Although i am not sure how to make the array hold the input value if the option selected is 2

Answer 1

You should not use Array if your amount of elements is not fixed. Instead, use List or ArrayList (subclass of List).

You can find all the methods you need at: developer.android.com/reference/java/util/ArrayList

EDIT 24/01/19:

If you need the List or ArrayList to be 10 by default just in case the user doesn't input a value, you can create an IF/ELSE which fills the List automatically or maybe use the SWITCH CASE you already have

For example:

List<Integer> myList = new ArrayList<Integer>();
float defaultValue = 0.0;

case 1:
    for(int i = 0; i < 10; i++) {
        myList.add(defaultValue)
    }
    break;
case 2:
    System.out.println("Enter the new size of array: ");
    int x = scan.nextInt();
    for(int i = 0; i < x; i++) {
        myList.add(defaultValue)
    }
    break;

Answer 2

You're not using the public Numbers (int size) constructor you've made in the Numbers class. Also you're creating a new variable called numbers, rather than assigning the local field obj. This:

    Numbers [] numbers = new Numbers[x];

should be

    obj = new Numbers(x);