This is working fine in IntelliJ but gets flagged on the create 2 small arrays... How come?

public static void main(String[] args) throws Exception {
        //write your code here
        int[] big = new int[20];
        BufferedReader r = new BufferedReader(new InputStreamReader(System.in));
        String s;

        for (int i = 0; i<20 ; i++){
            s = r.readLine();
            big[i] = Integer.parseInt(s);
        }

        int[] n1 = Arrays.copyOf(big, 10);
        int[] n2 = Arrays.copyOfRange(big, 10,20);

        for (int i=0;i<10;i++)
            System.out.println(n2[i]);
    }