1 00:00:00,950 --> 00:00:03,500 High they are not asked to have them all off. 2 00:00:03,510 --> 00:00:08,500 What we learned in the previous mess and so forth does them all a new class called JENNETT extra more 3 00:00:08,520 --> 00:00:13,340 has been created in the package column Dawk semantics quare.generics. 4 00:00:13,350 --> 00:00:17,140 OK now here is the main class on we are going to fill. 5 00:00:17,470 --> 00:00:22,290 So in the last lesson the Lubet agenda in is called Ask container. 6 00:00:22,470 --> 00:00:27,950 And we also saw that there was a generic class called store which implements container. 7 00:00:27,960 --> 00:00:33,270 So let's just go ahead and do that Fossel Let's create those generic types Husna to create a generic 8 00:00:33,270 --> 00:00:35,910 interface and Bynner created here 9 00:00:38,880 --> 00:00:40,220 and type B 10 00:00:43,950 --> 00:00:47,400 can also be what element but that's fine. 11 00:00:48,250 --> 00:00:49,560 And so that's the container 12 00:00:50,610 --> 00:00:58,420 . 13 00:01:03,910 --> 00:01:07,430 So you see this a 14 00:01:11,730 --> 00:01:16,620 and it's also right to get your return type would be geg 15 00:01:21,360 --> 00:01:21,760 set. 16 00:01:21,810 --> 00:01:24,660 So those are the two genetic types. 17 00:01:24,660 --> 00:01:28,550 Now let's go ahead and instantiate store. 18 00:01:28,770 --> 00:01:36,010 I'm Fussell let's create a stored off strength that storm strength sisig can dinner that have inspired 19 00:01:36,100 --> 00:01:41,140 be dinner because that's the interface and we need to do an interface. 20 00:01:41,140 --> 00:01:49,470 We know that going string store and let's use that diamond notation so that that type is automatically 21 00:01:49,470 --> 00:01:49,980 inferred 22 00:01:54,180 --> 00:01:59,350 shaila and that's printed code space. 23 00:01:59,510 --> 00:02:06,030 Be this not getting on this. 24 00:02:06,650 --> 00:02:09,140 Prince giallo OK. 25 00:02:09,630 --> 00:02:10,890 So that's what we have. 26 00:02:11,190 --> 00:02:16,710 And we know that genetics gives us the advantage of compile time by periphery. 27 00:02:16,800 --> 00:02:18,630 Right. 28 00:02:18,630 --> 00:02:23,440 So let's just go and cried to an integer here. 29 00:02:24,440 --> 00:02:31,320 And as you can see it says the Methot sex string in that type can a string is not applicable for the 30 00:02:31,320 --> 00:02:32,700 arguments. 31 00:02:33,180 --> 00:02:38,330 OK so it is giving us a compilation error right here at compilation time. 32 00:02:38,520 --> 00:02:43,480 OK so that's the main benefit of genetics right. 33 00:02:43,790 --> 00:02:51,390 It is commonly taught now that's created since it is genetics. 34 00:02:51,390 --> 00:02:57,600 We can create another instance of store but with the different type argument. 35 00:02:58,130 --> 00:03:02,030 So let's make it string sort of integer. 36 00:03:02,410 --> 00:03:04,160 That's called it. 37 00:03:04,860 --> 00:03:10,490 Do your store get in the mood got 38 00:03:14,070 --> 00:03:17,490 it run this is going to print one. 39 00:03:17,770 --> 00:03:18,390 OK. 40 00:03:18,780 --> 00:03:25,630 Now let's create a slightly more complicated instance. 41 00:03:26,370 --> 00:03:40,600 Let's make this list of integer k shift all its import data and its consciousness store. 42 00:03:40,930 --> 00:03:47,170 And once again the type is automatically inferred here and let's call it let's draw or 43 00:03:50,690 --> 00:03:52,540 not set. 44 00:03:53,100 --> 00:04:10,160 Let's use our Ariz class say eyes lest one do tree k and let's just say let's store not get here and 45 00:04:10,170 --> 00:04:14,470 this is going to print 1 2 and 3. 46 00:04:14,510 --> 00:04:15,070 OK. 47 00:04:15,420 --> 00:04:20,070 So that's how we can create instances. 48 00:04:20,070 --> 00:04:22,280 Now you might have a question. 49 00:04:22,320 --> 00:04:25,620 So what exactly is happening under the hood. 50 00:04:25,800 --> 00:04:31,390 Is it going to somehow create three instances of store for these three. 51 00:04:31,910 --> 00:04:37,700 I mean three start store process for when we are working with these different arguments. 52 00:04:37,710 --> 00:04:38,330 OK. 53 00:04:38,610 --> 00:04:46,290 Three store classes or is it simply creating store instances but somehow in the store instance you know 54 00:04:46,380 --> 00:04:48,200 the type would be string. 55 00:04:48,210 --> 00:04:51,870 In this case and in this case the object what how. 56 00:04:51,870 --> 00:04:55,110 Integer as the type for those variables here. 57 00:04:56,220 --> 00:04:59,560 OK and in this case it could be left off in two years. 58 00:04:59,620 --> 00:05:04,740 So we might guess if something like that is happening but that's not happening. 59 00:05:04,860 --> 00:05:12,650 OK so what is going to happen as a feature cart type eraser is being used here. 60 00:05:13,120 --> 00:05:20,800 And if you recall we said that Gen X is up your compile time concept which means that Gen X does not 61 00:05:20,800 --> 00:05:22,840 apply at runtime at runtime. 62 00:05:22,830 --> 00:05:25,220 There is no generates I don't care. 63 00:05:25,260 --> 00:05:26,720 And what does that mean. 64 00:05:26,740 --> 00:05:33,010 It means that the compiler basically uses this feature called Fraizer. 65 00:05:33,260 --> 00:05:33,740 OK. 66 00:05:33,780 --> 00:05:40,780 And as the name suggests it is going to it is that type C compiler is going to remove this type. 67 00:05:40,880 --> 00:05:43,110 OK so in this case it's a pipe argument. 68 00:05:43,260 --> 00:05:49,440 It's going to strip off this and it's just going to write as if this thing is not there and get a bite 69 00:05:49,440 --> 00:05:50,330 code. 70 00:05:50,500 --> 00:05:58,230 Similarly here also in this generic types since we are saying pipe eraser It is going to remove this 71 00:05:58,860 --> 00:05:59,980 type. 72 00:06:00,120 --> 00:06:06,120 OK and same here also it's going to strip this off and it's going to erase this off. 73 00:06:06,150 --> 00:06:07,960 That's why it's called IP razor. 74 00:06:08,070 --> 00:06:11,050 And for this be it were replaced by object. 75 00:06:11,070 --> 00:06:13,720 In this particular case here also object. 76 00:06:13,750 --> 00:06:15,300 See here. 77 00:06:15,390 --> 00:06:18,190 OK it's going to replace it object. 78 00:06:18,190 --> 00:06:23,880 Next we will also look at something called bonded parameters on there. 79 00:06:23,880 --> 00:06:30,960 This beacon extends some other glass in which case the clasp can be written here in this case you can 80 00:06:30,960 --> 00:06:36,030 think that the extents object in fact be extents object in this case internally. 81 00:06:36,030 --> 00:06:37,800 So it would replace that object. 82 00:06:37,810 --> 00:06:43,260 But if we extend something else then that would be stored here but that people look at it easier. 83 00:06:43,380 --> 00:06:47,010 But basically Typee treasure is that's all there is to type in Asia. 84 00:06:47,230 --> 00:06:49,040 So that's one thing that is going to happen. 85 00:06:49,060 --> 00:06:56,110 It's going to raise the type from both the parameterize types as well as from the type barometers. 86 00:06:56,130 --> 00:06:58,800 So it really object everything will be object here. 87 00:06:59,000 --> 00:07:05,400 And this whole thing will be stripped off but so this thing will also get stripped off. 88 00:07:05,670 --> 00:07:13,080 But here when we are getting in working to get the dirt get met that is going to return an object because 89 00:07:13,480 --> 00:07:16,880 here this is going to be replaced by object. 90 00:07:17,110 --> 00:07:23,050 And even the get out here is going to done an object since we are going to do it in an object. 91 00:07:23,380 --> 00:07:27,870 But in this particular invocation statement a string is being expected. 92 00:07:27,940 --> 00:07:37,980 So the the compiler would insert a cast here it would insert a string here like this and it would insert 93 00:07:37,990 --> 00:07:39,070 an integer here. 94 00:07:39,220 --> 00:07:42,570 I know over here it would insert a list of integer. 95 00:07:42,830 --> 00:07:45,520 OK so the compiler is going to do that. 96 00:07:45,570 --> 00:07:47,860 So compiler is doing two things. 97 00:07:47,910 --> 00:07:52,880 It is going to erase off all the pipes all the generics notations. 98 00:07:53,070 --> 00:07:56,490 And it is going to explicitly insert gas. 99 00:07:56,630 --> 00:07:57,280 OK. 100 00:07:57,570 --> 00:08:00,180 But for us the advantages the court is looking clean. 101 00:08:00,420 --> 00:08:06,420 But the court will not be that clean because it's going to insert gas and that is a magic pipe that 102 00:08:06,500 --> 00:08:08,660 compiler is doing for us. 103 00:08:08,700 --> 00:08:11,420 So that is what is going to happen under the hood. 104 00:08:11,910 --> 00:08:16,780 So all the pipes are getting erased and also costs are being inserted. 105 00:08:16,770 --> 00:08:18,670 That's how it's going to work. 106 00:08:18,660 --> 00:08:19,770 It might be confusing. 107 00:08:19,770 --> 00:08:21,430 Definitely it would be confusing. 108 00:08:21,490 --> 00:08:24,940 But that's on as happening with under the hood. 109 00:08:25,080 --> 00:08:25,320 OK. 110 00:08:25,320 --> 00:08:26,900 That S-type eraser. 111 00:08:27,450 --> 00:08:31,310 But we will look at Tipler later also towards the end of the chapter. 112 00:08:31,600 --> 00:08:34,430 But I think it will give you a good idea. 113 00:08:34,500 --> 00:08:39,450 That's why I wanted to discuss it now so that you would know what is actually happening under the hood 114 00:08:39,470 --> 00:08:39,740 . 115 00:08:39,920 --> 00:08:40,330 OK. 116 00:08:40,530 --> 00:08:46,030 Now there is a restriction that we also discussed about one of the restrictions was doc type argument 117 00:08:46,020 --> 00:08:47,400 can not be primitive. 118 00:08:47,670 --> 00:08:52,100 So let's try that out. 119 00:08:54,660 --> 00:08:57,120 Now as you can see we get a compiler error. 120 00:08:57,380 --> 00:08:58,020 OK. 121 00:08:58,260 --> 00:09:00,200 So that's not possible. 122 00:09:00,930 --> 00:09:09,270 And there was also a second restriction that we looked at that says that type parameter cannot be used 123 00:09:09,270 --> 00:09:10,940 in a static context. 124 00:09:11,010 --> 00:09:11,900 Right. 125 00:09:12,000 --> 00:09:20,610 So if you go here and if we make this Dodik it's going to get a compilation error cannot make a start 126 00:09:20,740 --> 00:09:23,710 reference to the non-static type. 127 00:09:24,270 --> 00:09:25,470 So that's what it is. 128 00:09:25,470 --> 00:09:27,230 So you cannot even do that. 129 00:09:27,750 --> 00:09:30,950 So those are the two restrictions that we have. 130 00:09:31,920 --> 00:09:39,490 And one other thing with this subtyping is sometimes you can if you want to you can also let's say if 131 00:09:39,550 --> 00:09:48,340 you want to make this a string then in that case you see it says add unimplemented metrics the type 132 00:09:48,350 --> 00:09:55,110 store must implement the inherited abstract method container holstering not such string. 133 00:09:55,170 --> 00:10:01,480 So it says that we need to implement this method called set which has a parameter string. 134 00:10:01,570 --> 00:10:06,540 So the moment we change this we need to implement some new methods. 135 00:10:06,750 --> 00:10:14,540 So let's go ahead and just this and as you can see some new methods got added which have strength. 136 00:10:14,710 --> 00:10:21,790 So just because we are saying that we want to implement content offspring then that would make us implement 137 00:10:22,240 --> 00:10:23,510 these methods. 138 00:10:23,770 --> 00:10:26,810 OK so that's what it is. 139 00:10:26,950 --> 00:10:35,920 But if you make it contain it on string then here over here the type argument has to be either string 140 00:10:36,460 --> 00:10:40,270 or a should not be anything in which case this needs to be remote. 141 00:10:40,300 --> 00:10:42,750 In which case it just cardless the wrong type. 142 00:10:42,760 --> 00:10:45,910 It's just it just means that the argument is not there. 143 00:10:46,090 --> 00:10:52,360 So it has to be either for doctype or it has to be string just because B how can you get off string 144 00:10:52,360 --> 00:10:53,060 here. 145 00:10:53,070 --> 00:10:59,830 OK so that's the restriction that people how you can also create out just make it some other type and 146 00:10:59,830 --> 00:11:08,230 you can also try it out for instance if you make a string here condense it off string as you can see 147 00:11:08,230 --> 00:11:08,740 here. 148 00:11:08,770 --> 00:11:10,410 It gives a compilation error. 149 00:11:10,710 --> 00:11:16,270 It says cannot infer type arguments for start and that's because we are using integer rather than string 150 00:11:16,270 --> 00:11:16,760 . 151 00:11:16,870 --> 00:11:22,930 So it's got to be a string on one off its subtypes Audix it's got to be a rock pipe and we will also 152 00:11:22,930 --> 00:11:28,990 discuss it by later which is basically doesn't have any arguments but it is dangerous to do that and 153 00:11:28,990 --> 00:11:30,700 we will discuss that later. 154 00:11:30,700 --> 00:11:33,090 So just wanted to highlight that. 155 00:11:33,250 --> 00:11:43,790 So let me just go ahead and make this the very Modise auto created methods. 156 00:11:44,080 --> 00:11:46,540 So that's about what we learned earlier. 157 00:11:46,750 --> 00:11:55,000 But let's also go ahead and create a few more but I'm impressed by a few more instances just as it's 158 00:11:55,000 --> 00:12:02,490 created a list off member number as a class and the set list. 159 00:12:04,000 --> 00:12:09,510 New Order list and Khrushchev. 160 00:12:09,560 --> 00:12:20,950 Oh and and yes we can I add an ember instance of number or one off it's spazzes subprocess. 161 00:12:20,980 --> 00:12:24,230 And this is one of the subclauses integer. 162 00:12:24,250 --> 00:12:27,190 So we can do dot on that say 1. 163 00:12:27,690 --> 00:12:28,010 OK. 164 00:12:28,030 --> 00:12:34,110 So in this list are Ls to be an odd number or we can add one ifits subtype objects. 165 00:12:34,300 --> 00:12:38,870 Similarly double it is also a subtype off number. 166 00:12:39,100 --> 00:12:51,790 So you can just say double and to do OK but you cannot add anything else because we are using generics 167 00:12:51,790 --> 00:12:51,840 . 168 00:12:51,880 --> 00:12:56,710 So you cannot do something like this strain. 169 00:12:56,870 --> 00:13:03,490 And it's going to do on the compile time type safety kicks in and says you cannot do that. 170 00:13:03,700 --> 00:13:10,750 The method out of number in that type list off number is is not applicable for the argument string because 171 00:13:10,750 --> 00:13:14,110 we are passing a number here and I admit the third one now. 172 00:13:14,130 --> 00:13:17,030 Because of this it well how. 173 00:13:17,030 --> 00:13:18,550 Number Aztek type. 174 00:13:18,820 --> 00:13:24,250 And if we try to add a string object it's going to give us this combination error. 175 00:13:24,730 --> 00:13:25,260 OK. 176 00:13:25,330 --> 00:13:26,590 That's the issue. 177 00:13:26,590 --> 00:13:27,580 That's the thing. 178 00:13:27,710 --> 00:13:29,420 And that's the benefit that we have. 179 00:13:29,440 --> 00:13:32,380 But give it a bit generics. 180 00:13:32,380 --> 00:13:36,600 Now let's also do something with Arrius 181 00:13:39,730 --> 00:13:42,250 say you list off too. 182 00:13:42,280 --> 00:13:44,480 So it does list on either side. 183 00:13:45,010 --> 00:13:45,470 OK. 184 00:13:45,490 --> 00:13:52,390 So what it means is you can store any of the list implementations list as an interface and we can store 185 00:13:52,380 --> 00:14:02,600 any off its implementations and just say zero on that door New Artist. 186 00:14:02,620 --> 00:14:11,920 OK another just object is being stored at the zero position and one that can store that's a linked list 187 00:14:13,050 --> 00:14:19,530 and that is one game we can do got a whole game. 188 00:14:19,870 --> 00:14:23,220 So that's because we can store any list. 189 00:14:23,250 --> 00:14:24,010 OK. 190 00:14:24,100 --> 00:14:30,460 Now if you make this an idealist then B how. 191 00:14:30,610 --> 00:14:32,950 I mean we don't get any competition at her. 192 00:14:33,430 --> 00:14:37,210 OK what this means is we want to store only our A-list within this array. 193 00:14:37,450 --> 00:14:41,130 But we are also starting ringless but it did not give us a completion order. 194 00:14:41,320 --> 00:14:47,970 But if we run it it's going to give this or a story exception game which means that at runtime we are 195 00:14:47,980 --> 00:14:53,800 getting this exception and that's not very good because the type safety is not enforced or compile time 196 00:14:53,830 --> 00:14:54,980 but at runtime. 197 00:14:55,210 --> 00:14:55,710 OK. 198 00:14:55,840 --> 00:14:57,590 That we are going to discuss later. 199 00:14:57,730 --> 00:15:04,090 But I just wanted to just show you that if you create like an artist here or something you can store 200 00:15:04,270 --> 00:15:11,830 either that instance of doc type or I want to get subtypes but back then and then if you're trying to 201 00:15:11,830 --> 00:15:14,510 store something as we are getting a compiler error OK. 202 00:15:14,530 --> 00:15:22,660 So the error is being shown at compile time itself whereas in case of an NRA we can see that we are 203 00:15:22,650 --> 00:15:28,200 not having any issue at compile time because we are supposed to store only our oldest objects. 204 00:15:28,400 --> 00:15:30,760 And here we are storing l'Anglaise. 205 00:15:30,760 --> 00:15:38,110 But in case of an array the typesafe B is being enforced only at runtime behere the types is enforced 206 00:15:38,110 --> 00:15:40,080 at compile time in case of generics. 207 00:15:40,140 --> 00:15:47,140 But we are as it is enforced at runtime and that we will also discuss later when we are discussing invariants 208 00:15:47,130 --> 00:15:47,520 . 209 00:15:47,530 --> 00:15:49,870 But just wanted to highlight that here. 210 00:15:50,050 --> 00:15:50,980 So that's about it. 211 00:15:51,120 --> 00:15:51,690 Thank you. 212 00:15:51,730 --> 00:15:54,640 And the court is available in the resources section happy coding