1 00:00:01,140 --> 00:00:08,970 Let's not implement couple of manager classes if you recall manager classes include business logic which 2 00:00:08,970 --> 00:00:12,130 would include code to instantiate entities. 3 00:00:12,570 --> 00:00:18,840 So they'll begin creating manager classes by writing methods that would instantiate entities that we 4 00:00:18,840 --> 00:00:20,140 created. 5 00:00:20,520 --> 00:00:26,050 The methods we laid will be used later from the day dustoff class which we rewrite later. 6 00:00:26,790 --> 00:00:31,750 The manager classes we will write will be named as User Manager and bookmark manager. 7 00:00:32,340 --> 00:00:35,850 USE IT manager will good business logic related to users. 8 00:00:35,960 --> 00:00:40,630 Well the plant manager billing good business logic related to bookmarks. 9 00:00:40,650 --> 00:00:44,820 One main thing to note about Manager classes is that they are stateless. 10 00:00:44,940 --> 00:00:51,330 That is they don't mean in any instance variables so you don't need to create an instance of them and 11 00:00:51,330 --> 00:00:55,950 instead can maintain them as static utility classes. 12 00:00:56,040 --> 00:01:04,620 However for managers it's recommended to not use static utility classes instead of just one single instance 13 00:01:04,950 --> 00:01:07,690 of each of the manager classes. 14 00:01:07,710 --> 00:01:14,900 The reason for this is in some projects manager classes implement an interface and indorsing not yours 15 00:01:14,900 --> 00:01:15,230 . 16 00:01:15,270 --> 00:01:22,920 You cannot use tactic utility classes as static matters in such classes cannot override or hide instance 17 00:01:22,920 --> 00:01:24,560 methods in an interface. 18 00:01:25,260 --> 00:01:31,630 So the recommended method is to create a single instance of the manager class and this is achieved by 19 00:01:31,650 --> 00:01:38,190 using a design pattern called Singleton partan a singleton pattern is simply a design pattern that would 20 00:01:38,280 --> 00:01:42,270 ensure that exactly one object is created or no more. 21 00:01:42,550 --> 00:01:49,720 And it also provides a global point to access the object store manager classes are basically singletons 22 00:01:49,730 --> 00:01:50,180 . 23 00:01:50,970 --> 00:01:55,010 So let's get started and see how this is done. 24 00:01:55,410 --> 00:01:58,580 Krust let's create a new package for our managers. 25 00:01:59,040 --> 00:02:02,620 So let's just right click here. 26 00:02:06,300 --> 00:02:07,890 So it would be calm semantics. 27 00:02:07,910 --> 00:02:09,570 There really are dock managers 28 00:02:12,300 --> 00:02:14,640 let's begin with creating the user manager Plus 29 00:02:22,320 --> 00:02:24,930 just a short note on the naming convention here. 30 00:02:25,230 --> 00:02:30,680 Fund manager is typically the last names would end with the manager. 31 00:02:30,720 --> 00:02:36,260 Some programmers also use the term service instead of manager as managers to define the service here 32 00:02:36,270 --> 00:02:37,150 . 33 00:02:37,200 --> 00:02:42,780 However it's just a matter of choice and in my opinion it's really not important whether we use the 34 00:02:42,780 --> 00:02:49,530 term manager ourselves to end the class name only important thing to do as follow what your team is 35 00:02:49,530 --> 00:02:50,150 doing. 36 00:02:50,400 --> 00:02:52,920 If your team is using manager then go with manager. 37 00:02:53,130 --> 00:02:55,950 If your team is using service then go with service. 38 00:02:56,430 --> 00:03:03,660 OK first let's implement a singleton related code as part of implementing Singleton we to have a private 39 00:03:03,660 --> 00:03:04,690 constructor. 40 00:03:05,130 --> 00:03:11,050 So let's create a private constructor. 41 00:03:11,370 --> 00:03:17,700 We know that having a private constructor implies that one cannot instantiate the class so the class 42 00:03:17,700 --> 00:03:22,060 of user manager cannot create an instance of User Manager. 43 00:03:22,140 --> 00:03:24,170 So that's what we want for a singleton. 44 00:03:24,180 --> 00:03:27,920 We don't want our clients to create instances freely. 45 00:03:28,050 --> 00:03:32,270 So for Singleton we said that only one object needs to be created. 46 00:03:32,580 --> 00:03:37,530 Now since it's a private constructor we cannot create an instance of it. 47 00:03:37,560 --> 00:03:41,890 Now how do you create that single instance for a singleton. 48 00:03:41,970 --> 00:03:48,510 So for that only way to do it as since it's a private constructor the single object has to be created 49 00:03:48,510 --> 00:03:50,220 from within this class. 50 00:03:50,220 --> 00:03:53,130 So that's done from a method and we can. 51 00:03:53,130 --> 00:03:58,700 The convention is to collect as get instance. 52 00:03:59,250 --> 00:04:07,220 Now this method has to return an object of type user manager. 53 00:04:07,540 --> 00:04:11,220 OK so that's the return type. 54 00:04:11,220 --> 00:04:18,270 Now that needs to be public since one cannot create an instance of user manager. 55 00:04:18,270 --> 00:04:20,310 It needs to be a static method. 56 00:04:20,940 --> 00:04:26,930 So this is the method that would return the single instance of user manager. 57 00:04:27,300 --> 00:04:31,670 OK so that and Ipperwash the global point of access. 58 00:04:31,710 --> 00:04:37,290 Now you can create an instance here but let's do it here. 59 00:04:37,830 --> 00:04:45,990 So let's create a pirate variable that type of that variable has to be user manager and it's call the 60 00:04:45,990 --> 00:04:48,030 variable as instance. 61 00:04:48,350 --> 00:04:52,030 And let's create the instance here. 62 00:04:52,060 --> 00:04:52,550 Sorry 63 00:04:57,060 --> 00:05:04,820 Now since this is an instance variable we cannot access it from here so is if we want to access it from 64 00:05:04,820 --> 00:05:05,680 a static method. 65 00:05:05,690 --> 00:05:07,840 It needs to be static too. 66 00:05:08,690 --> 00:05:12,730 So that's how we create an instance or we can actually create it here also. 67 00:05:12,950 --> 00:05:16,070 But we are creating it here in the declaration itself. 68 00:05:16,130 --> 00:05:23,350 So over here all we do as we're done instance. 69 00:05:24,360 --> 00:05:32,030 So now what happens is whenever the client code says User Manager Daag get instance on the very first 70 00:05:32,030 --> 00:05:36,730 time it does that the JVM actually loads the class Lord of Lords. 71 00:05:36,760 --> 00:05:41,790 Does the user manager class into memory at the same time it will also exit your desk. 72 00:05:42,020 --> 00:05:45,950 The first statement and an instance will be created. 73 00:05:45,990 --> 00:05:51,200 So that happens when the when this method is invoked for the very first time. 74 00:05:51,290 --> 00:05:56,450 So by the time the method is invoked the instance variable is already initialized with the object. 75 00:05:56,560 --> 00:06:03,320 OK and we are just returning the object and this is a good way of creating the singleton. 76 00:06:04,000 --> 00:06:08,410 You know there are a couple of other minor variations also for creating singletons. 77 00:06:08,710 --> 00:06:15,200 I mean once you are done with the course you can check out Chapter 5 and head first design patterns 78 00:06:15,200 --> 00:06:15,470 book. 79 00:06:15,480 --> 00:06:21,770 It's a very good book and you can check out the chapter 5 which is on specif specifically for us on 80 00:06:21,770 --> 00:06:26,930 singletons and it explains these other minor variations also. 81 00:06:27,020 --> 00:06:33,520 So but the approach we followed is good and you can follow this approach. 82 00:06:33,950 --> 00:06:36,440 So that's how you create a singleton. 83 00:06:36,590 --> 00:06:44,710 Next let's create a method for instantiating user Blake user. 84 00:06:45,290 --> 00:06:46,230 Let's call the methods. 85 00:06:46,380 --> 00:06:51,520 Create users since we want to create an user instance. 86 00:06:51,750 --> 00:06:55,940 So that's how all the instance variables. 87 00:06:56,080 --> 00:06:57,870 Let's click on this. 88 00:06:57,870 --> 00:07:04,220 So these are the variables ID email password so id is long 89 00:07:20,390 --> 00:07:24,350 and user type. 90 00:07:24,360 --> 00:07:27,850 So this method will be invoked later from the dust or class 91 00:07:30,570 --> 00:07:31,920 of. 92 00:07:32,300 --> 00:07:33,900 So what we have. 93 00:07:34,160 --> 00:07:38,940 And so let's go ahead and say user user 94 00:07:42,660 --> 00:07:44,010 now a user 95 00:07:48,800 --> 00:07:49,300 id 96 00:07:55,730 --> 00:07:58,260 say trust me 97 00:08:14,270 --> 00:08:21,860 you think we missed the password here or said email. 98 00:08:21,990 --> 00:08:25,460 So Id email password first name last name 99 00:08:28,500 --> 00:08:31,440 and gender and user name. 100 00:08:31,500 --> 00:08:33,810 So we have all of them sent here. 101 00:08:33,920 --> 00:08:46,970 So let's just say written user so that the User Manager class next lets create a bookmark manager and 102 00:08:47,070 --> 00:08:47,850 managers 103 00:08:47,850 --> 00:08:57,130 . 104 00:08:57,530 --> 00:08:59,860 So once again thats create a singleton 105 00:09:03,070 --> 00:09:05,030 thats the private constructor 106 00:09:11,380 --> 00:09:24,730 its the public access matter private static. 107 00:09:28,090 --> 00:09:32,660 So just just returns the instance. 108 00:09:33,150 --> 00:09:40,110 Ok so thats the singleton code for creating Singleton host lets create the movie method to create a 109 00:09:40,110 --> 00:09:45,540 movie. 110 00:09:49,160 --> 00:09:59,910 Just open the movie Close but Mark has some valuable Speidel and profile you are in a 111 00:10:08,070 --> 00:10:09,630 movie class as a release. 112 00:10:09,650 --> 00:10:11,830 Your cast director's 113 00:10:26,420 --> 00:10:28,160 gender and I am beby rating 114 00:10:32,640 --> 00:10:39,690 . 115 00:10:40,280 --> 00:10:43,070 So let's just go ahead and create the movie instance 116 00:10:46,500 --> 00:10:52,220 in that same boat movie we movie 117 00:10:56,000 --> 00:10:58,650 you know said the loose 118 00:11:11,210 --> 00:11:12,110 release either 119 00:11:28,050 --> 00:11:29,760 so I guess that's about it. 120 00:11:29,810 --> 00:11:33,010 So it's a certain movie. 121 00:11:33,020 --> 00:11:36,640 So that's how you would create a movie. 122 00:11:36,650 --> 00:11:43,040 Similarly we need to create methods for creating both book and also grappling instances. 123 00:11:43,220 --> 00:11:48,340 So in the interest of time I'm not going to the monsters creating those matters as that pretty identical 124 00:11:48,390 --> 00:11:48,700 . 125 00:11:49,010 --> 00:11:51,810 So just go ahead and create them yourself. 126 00:11:51,810 --> 00:11:57,680 I will also do it offline and we'll come back to just show you the quarter. 127 00:11:59,420 --> 00:12:05,940 So here is the Create book method and it's creating a book instance and setting all the feels like the 128 00:12:05,930 --> 00:12:11,240 ID title publication your publisher authors genré iron Amazon rating. 129 00:12:11,580 --> 00:12:18,410 OK so that's the book instance and here is the method create weblink and we are creating an instance 130 00:12:18,410 --> 00:12:26,510 of a blank on one side inserting ID tightly and the two feel specific to Webling which are you out host 131 00:12:26,510 --> 00:12:26,950 . 132 00:12:27,410 --> 00:12:29,630 So those are the two manager classes. 133 00:12:29,750 --> 00:12:33,220 Later we'll be adding more code to these two classes.