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These are the user uploaded subtitles that are being translated: 1 1 00:00:00,212 --> 00:00:02,716 (bright music) 2 2 00:00:02,716 --> 00:00:05,310 (light typing) 3 3 00:00:05,310 --> 00:00:06,143 In this section, 4 4 00:00:06,143 --> 00:00:08,080 we're going to look at lists. 5 5 00:00:08,080 --> 00:00:12,530 The list is an abstract data type and in the next video, 6 6 00:00:12,530 --> 00:00:16,510 we're going to go over what an abstract data type is. 7 7 00:00:16,510 --> 00:00:19,270 So a list isn't a concrete data structure, 8 8 00:00:19,270 --> 00:00:21,150 it's an abstract data type. 9 9 00:00:21,150 --> 00:00:23,140 And when it comes to abstract data types, 10 10 00:00:23,140 --> 00:00:25,130 normally there's an interface involved 11 11 00:00:25,130 --> 00:00:27,360 and list is no exception. 12 12 00:00:27,360 --> 00:00:30,820 In Java, the lists that we're gonna look at in this section 13 13 00:00:30,820 --> 00:00:34,410 all implement the java.util.list interface, 14 14 00:00:34,410 --> 00:00:36,500 so that's what I have on this screen. 15 15 00:00:36,500 --> 00:00:39,550 Classes that implement the list interface represent 16 16 00:00:39,550 --> 00:00:42,950 an ordered collection also known as a sequence. 17 17 00:00:42,950 --> 00:00:45,630 There are quite a few classes that implement list. 18 18 00:00:45,630 --> 00:00:47,100 We're not gonna look at all of them. 19 19 00:00:47,100 --> 00:00:48,880 We are gonna look at a few. 20 20 00:00:48,880 --> 00:00:50,870 We're gonna look at array list. 21 21 00:00:50,870 --> 00:00:53,870 We're going to look linked list. 22 22 00:00:53,870 --> 00:00:55,670 We'll look at those two in this section. 23 23 00:00:55,670 --> 00:00:57,240 We're also gonna look at vector. 24 24 00:00:57,240 --> 00:00:59,620 There's also an abstract list class 25 25 00:00:59,620 --> 00:01:01,880 and an abstract sequential list. 26 26 00:01:01,880 --> 00:01:05,440 If you want to implement the list interface, 27 27 00:01:05,440 --> 00:01:08,000 you want to create a custom implementation 28 28 00:01:08,000 --> 00:01:12,420 rather than starting with list itself and implementing that, 29 29 00:01:12,420 --> 00:01:15,450 it's a good idea to instead extend abstract list 30 30 00:01:15,450 --> 00:01:16,970 and abstract sequential list 31 31 00:01:16,970 --> 00:01:19,450 because there are scoledo implementations 32 32 00:01:19,450 --> 00:01:21,520 of the list interface and so they kind of give you 33 33 00:01:21,520 --> 00:01:25,320 a head start and all you have to do is override the methods 34 34 00:01:25,320 --> 00:01:27,570 that you specifically want to implement 35 35 00:01:27,570 --> 00:01:29,270 if you want custom behaviour. 36 36 00:01:29,270 --> 00:01:32,760 So if you are going to implement a custom list, 37 37 00:01:32,760 --> 00:01:35,500 its a good idea to extend one of these two classes. 38 38 00:01:35,500 --> 00:01:39,000 So lets just look at a few of the methods in here. 39 39 00:01:39,000 --> 00:01:43,160 You'll see we have add, so we can add items to the list. 40 40 00:01:43,160 --> 00:01:47,260 We can check to see whether a list contains an object. 41 41 00:01:47,260 --> 00:01:51,690 We can get an object from the list if we have its index. 42 42 00:01:51,690 --> 00:01:54,190 We can find the index of an object in the list. 43 43 00:01:54,190 --> 00:01:56,273 We can check whether a list is empty. 44 44 00:01:57,350 --> 00:01:59,580 We can remove objects from the list. 45 45 00:01:59,580 --> 00:02:01,870 We can find out using the size method 46 46 00:02:01,870 --> 00:02:03,500 how many items are in the list 47 47 00:02:03,500 --> 00:02:07,750 and we can get the array that's backing a list 48 48 00:02:07,750 --> 00:02:09,640 and we're gonna see what that means 49 49 00:02:09,640 --> 00:02:11,470 in the next couple of videos. 50 50 00:02:11,470 --> 00:02:15,500 Now some of the classes we're gonna look at in this section, 51 51 00:02:15,500 --> 00:02:17,990 like array list, you've probably worked with before. 52 52 00:02:17,990 --> 00:02:20,470 Array list is a really popular class 53 53 00:02:20,470 --> 00:02:21,830 but we're gonna dig a little deeper. 54 54 00:02:21,830 --> 00:02:24,100 We're gonna actually look at some of the array list code 55 55 00:02:24,100 --> 00:02:26,280 to see what's going on under the covers. 56 56 00:02:26,280 --> 00:02:29,120 Okay, so when we're dealing with lists, 57 57 00:02:29,120 --> 00:02:32,020 we're dealing with an ordered sequence, 58 58 00:02:32,020 --> 00:02:33,970 so the data is organised sequentially 59 59 00:02:33,970 --> 00:02:36,610 just as it is in an array and we're gonna see 60 60 00:02:36,610 --> 00:02:40,430 in a couple of videos that a popular way to implement 61 61 00:02:40,430 --> 00:02:42,730 the list interface is to use an array. 62 62 00:02:42,730 --> 00:02:44,820 So let's move on now and take a quick look 63 63 00:02:44,820 --> 00:02:46,860 at what an abstract data type is. 64 64 00:02:46,860 --> 00:02:48,410 I'll see you in the next video. 5601