1
00:00:00,210 --> 00:00:05,490
We need to forbid the caller from misusing Method's or constructor's, the constructor doesn't receive

2
00:00:05,490 --> 00:00:07,689
any parameters, so nothing to check here.

3
00:00:08,250 --> 00:00:10,230
There is nothing a quality control in the center.

4
00:00:10,580 --> 00:00:13,040
All of them would already through a null pointer exception.

5
00:00:13,050 --> 00:00:15,570
So throwing our own exception would be redundant.

6
00:00:16,290 --> 00:00:18,590
Same can be said for removing checkout.

7
00:00:18,600 --> 00:00:23,910
We don't need to check for a legal argument exceptions, but these methods are vulnerable to being called

8
00:00:23,910 --> 00:00:24,770
at a bad time.

9
00:00:24,930 --> 00:00:30,960
For example, if a cart object doesn't have any items, then it's not in a legal state to call or remove

10
00:00:30,960 --> 00:00:31,790
or check out.

11
00:00:32,280 --> 00:00:36,880
You can't remove items if there aren't any and you can't check out an empty cart.

12
00:00:37,650 --> 00:00:40,500
So what we'll do is say if items that is empty.

13
00:00:45,530 --> 00:00:47,870
Throw a new illegal state exception.

14
00:00:50,270 --> 00:00:52,670
Cannot remove items from an empty cart.

15
00:01:04,290 --> 00:01:08,460
We can do the same thing for the check out action if items that is empty.

16
00:01:12,340 --> 00:01:14,530
There were new illegal state exception.

17
00:01:18,620 --> 00:01:20,540
Cannot check out an empty cart.

18
00:01:21,520 --> 00:01:26,620
As far as I know, that's all the quality control that we need to apply and both methods are going to

19
00:01:26,620 --> 00:01:28,680
forbid the caller from misusing them.