如何测试使用默认容量和固定容量的ArrayList的有效性

Question

    public class TestListAdd {

    public static void main(String[] args) {
        System.out.println("Test 10000000 List add start");
        System.out.println("10000000 Capacity: "+ listAdd(10000000,10000000));
        System.out.println("Default Capacity: "+ listAdd(10000000));
    }

    public static Long listAdd(int num){
        Long starTime = System.currentTimeMillis();
        List<Object> list = new ArrayList<>();
        for (Integer i = 0; i < num-1; i++) {
            list.add(1);
        }
        Long endTime = System.currentTimeMillis();
        return endTime - starTime;
    }

    public static Long listAdd(int capatity,int num){
        Long starTime = System.currentTimeMillis();
        List<Object> list = new ArrayList<>(capatity);
        for (Integer i = 0; i < num-1; i++) {
            list.add(1);
        }
        Long endTime = System.currentTimeMillis();
        return endTime - starTime;
    }
}

结果

测试10000000列表添加开始

Default Capacity: 2350
10000000 Capacity: 455

但是我改变位置，然后我发现它不正确

Test 10000000 List add start
10000000 Capacity: 2100
Default Capacity: 950