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(bright music) 2

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(light typing) 3

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In this section, 4

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we're going to look at lists. 5

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The list is an abstract data type and in the next video, 6

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we're going to go over what an abstract data type is. 7

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So a list isn't a concrete data structure, 8

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it's an abstract data type. 9

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And when it comes to abstract data types, 10

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normally there's an interface involved 11

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and list is no exception. 12

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In Java, the lists that we're gonna look at in this section 13

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all implement the java.util.list interface, 14

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so that's what I have on this screen. 15

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Classes that implement the list interface represent 16

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an ordered collection also known as a sequence. 17

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There are quite a few classes that implement list. 18

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We're not gonna look at all of them. 19

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We are gonna look at a few. 20

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We're gonna look at array list. 21

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We're going to look linked list. 22

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We'll look at those two in this section. 23

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We're also gonna look at vector. 24

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There's also an abstract list class 25

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and an abstract sequential list. 26

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If you want to implement the list interface, 27

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you want to create a custom implementation 28

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rather than starting with list itself and implementing that, 29

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it's a good idea to instead extend abstract list 30

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and abstract sequential list 31

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because there are scoledo implementations 32

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of the list interface and so they kind of give you 33

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a head start and all you have to do is override the methods 34

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that you specifically want to implement 35

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if you want custom behaviour. 36

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So if you are going to implement a custom list, 37

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its a good idea to extend one of these two classes. 38

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So lets just look at a few of the methods in here. 39

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You'll see we have add, so we can add items to the list. 40

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We can check to see whether a list contains an object. 41

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We can get an object from the list if we have its index. 42

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We can find the index of an object in the list. 43

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We can check whether a list is empty. 44

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We can remove objects from the list. 45

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We can find out using the size method 46

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how many items are in the list 47

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and we can get the array that's backing a list 48

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and we're gonna see what that means 49

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in the next couple of videos. 50

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Now some of the classes we're gonna look at in this section, 51

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like array list, you've probably worked with before. 52

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Array list is a really popular class 53

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but we're gonna dig a little deeper. 54

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We're gonna actually look at some of the array list code 55

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to see what's going on under the covers. 56

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Okay, so when we're dealing with lists, 57

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we're dealing with an ordered sequence, 58

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so the data is organised sequentially 59

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just as it is in an array and we're gonna see 60

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in a couple of videos that a popular way to implement 61

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the list interface is to use an array. 62

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So let's move on now and take a quick look 63

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at what an abstract data type is. 64

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I'll see you in the next video.