Почему 2 раза?

public class Solution {
    public static void main(String[] args) {
        System.out.println(getInsertTimeInMs(new ArrayList()));
        System.out.println(getInsertTimeInMs(new LinkedList()));
    }

    public static long getInsertTimeInMs(List list) {
        Date date = new Date();
        insert10000(list);

        Date date2 = new Date();
        long a = date2.getTime() - date.getTime();
        System.out.println(a);
        return a;
    }

    public static void insert10000(List list) {
        for (int i = 0; i < 10000; i++) {
            list.add(0, new Object());
        }
    }
}
        for (int i = 0; i < 10000; i++) {
            list.add(0, new Object());
        }
    }
}