Cannot invoke get(int) on the array type ArrayList<Integer>[], even though the get method is applicable to ArrayLists

Question

I'm writing a method that takes an ArrayList and uses the element at a certain index in a different location , yet when I use the .get(int) method in the code, I get an error.

static void linreg(ArrayList<Integer> x[], ArrayList<Integer> y[]) {

        double sum_x = 0, sum_y = 0, int n = 15;
        
        for (int i = 0; i < n; i++) {

          sum_x += x.get(i); - Cannot invoke get(int) on the array type ArrayList<Integer>[]
          sum_y += y.get(i); - Cannot invoke get(int) on the array type ArrayList<Integer>[]

Is there a way to fix this? Thanks

Side note: it is usually much better to do a List<List<Integer>> construct than to mix arrays with lists as you're trying to do. — Hovercraft Full Of Eels
– Hovercraft Full Of Eels, Commented Aug 25, 2021 at 1:04

VHS · Accepted Answer · 2021-08-25 00:21:56Z

2

The parameters x and y are arrays. Arrays in java don't have a get method. That's why you get the error. You don't even need them as arrays. You just need them as lists which do have get method.

static void linreg(List<Integer> x, List<Integer> y) {

        double sum_x = 0, sum_y = 0, int n = 15;
        
        for (int i = 0; i < n; i++) {

          sum_x += x.get(i); 
          sum_y += y.get(i);
        }
        System.out.println(sum_x);
        System.out.println(sum_y);
 }

answered Aug 25, 2021 at 0:21

VHS

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Unmitigated · Accepted Answer · 2021-08-25 00:20:04Z

2

x is not of type ArrayList<Integer>, it is of type ArrayList<Integer>[]. (Note that it is not recommended to use this syntax exactly because of the confusion you had.) Perhaps you didn't mean to have both an array and a list.

edited Aug 25, 2021 at 0:20

Unmitigated

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answered Aug 25, 2021 at 0:17

chrylis -cautiouslyoptimistic-

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