WEBVTT 00:00.170 --> 00:00.770 Hi everyone. 00:00.770 --> 00:02.090 Welcome back to this tutorial. 00:02.090 --> 00:08.510 In this tutorial we will code and explore the map method, flat map method and the filter method that 00:08.510 --> 00:10.820 are part of the optional class. 00:10.850 --> 00:19.730 The first step is I'm going to create a class called Optional map Flat Map example. 00:20.000 --> 00:24.020 Let's make this class executable by adding public static void main method. 00:24.350 --> 00:29.540 So the methods that we are going to explore this presentation mode. 00:31.220 --> 00:38.090 Are going to be filter flat, map and map. 00:38.240 --> 00:42.230 So the first method that we are going to take a look at is a filter method. 00:42.560 --> 00:42.950 Right. 00:42.950 --> 00:49.610 I'm going to create a method specific for this one, and this method is not going to return anything 00:49.790 --> 00:54.950 and then the method name is going to be optional filter. 00:55.910 --> 00:58.700 So I'm going to use the student database. 01:00.380 --> 01:07.460 Dart Pyrone supplier Dart get this is going to give me the actual student. 01:07.760 --> 01:12.920 And then we are going to encapsulate that inside the optional object. 01:12.920 --> 01:18.830 So this will return optional of type student. 01:18.860 --> 01:19.610 Right. 01:19.610 --> 01:24.590 The next step is let's get this value optional of student. 01:25.100 --> 01:27.160 Let's give it a name, right? 01:27.170 --> 01:30.350 The name is going to be let's import the student. 01:32.210 --> 01:34.430 The name is going to be student optional. 01:34.460 --> 01:35.040 There you go. 01:35.060 --> 01:41.630 So we have the student optional, which has a student inside it, and the student is going to be Adam. 01:43.080 --> 01:45.600 Now you want to apply some filter, right? 01:45.600 --> 01:51.090 So filter is some operation which we have seen in the previous tutorials as part of the stream operation. 01:51.090 --> 01:55.050 Now optional also have a filter method that it supports. 01:55.050 --> 01:58.410 If you want to apply some filter before you get to the actual value. 01:58.410 --> 02:06.090 So what I'm going to do, I'm going to do student optional dot filter so you can pass a predicate. 02:06.120 --> 02:08.310 The predicate that I'm going to use. 02:08.340 --> 02:16.200 We all know this optional object encapsulate a student, so I'm going to use a student student dot get 02:16.210 --> 02:20.250 GPA greater than or equal to 3.5. 02:20.250 --> 02:23.100 So I'm going to give the value as 3.5. 02:23.130 --> 02:25.710 If that is there, then. 02:26.900 --> 02:28.740 I'm going to build a pipeline here. 02:28.770 --> 02:31.050 If that is there, then do a. 02:32.610 --> 02:38.070 If present, then print the student. 02:40.620 --> 02:42.580 Now let's go ahead and run this one. 02:42.600 --> 02:48.220 So in the public static void main method, I'm going to call the optional filter method. 02:48.240 --> 02:49.860 This is going to. 02:51.540 --> 02:53.050 Check the student GPA. 02:53.050 --> 02:59.080 If it is greater than 3.5, then it is going to get access to that student object and then printing 02:59.080 --> 02:59.230 it. 02:59.230 --> 03:03.220 If you want some other operation that needs to be performed, you are welcome to do it. 03:03.220 --> 03:05.920 But in here I want to keep this example really simple. 03:05.920 --> 03:08.020 That's the reason why I'm just printing it here. 03:08.170 --> 03:10.420 Let's go ahead and check what is the student's GPA? 03:10.450 --> 03:10.900 GPA? 03:10.930 --> 03:12.730 The GPA is 3.6, right? 03:12.760 --> 03:16.420 Let's say I'm going to give the value as 4.2. 03:17.110 --> 03:23.800 So in that case, nothing will happen because this filter is going to filter out the student and the 03:23.800 --> 03:27.520 student won't even reach the if present method. 03:28.000 --> 03:28.570 Right? 03:28.570 --> 03:31.060 So this is all about the filter method. 03:31.060 --> 03:38.410 The filter method gives you the flexibility to apply the filter operations on an optional object. 03:38.410 --> 03:41.260 Again, this is not a stream, this is an optional object. 03:41.290 --> 03:44.980 Now let's go ahead and explore the map method. 03:44.980 --> 03:50.750 I'm going to come to the flatMap method in a bit, but we'll explore the map method. 03:50.750 --> 03:55.130 We talked about map method and we covered map method a bit in the previous tutorial. 03:55.130 --> 03:58.490 I'm just going to give you the similar kind of example. 03:58.490 --> 03:59.690 Nothing new here. 03:59.690 --> 04:07.580 So what I'm going to do, I'm going to do, I'm going to create a method public static void, and then 04:07.580 --> 04:10.010 this is going to be optional map. 04:11.580 --> 04:14.580 And I'm going to do the same operation here. 04:15.510 --> 04:22.770 So now we have access to the optional method in here, what we are going to do. 04:24.620 --> 04:26.900 Now we have the optional student ready. 04:26.930 --> 04:30.350 The next step is we are going to check if the student is present. 04:31.670 --> 04:32.240 Right. 04:32.240 --> 04:33.530 That should be the first check. 04:33.560 --> 04:38.720 Then what we are going to do, we are going to get the name of the student or you can apply. 04:38.720 --> 04:41.480 We can change this one with the filter also. 04:41.630 --> 04:42.680 Let's go ahead and do that. 04:42.710 --> 04:50.930 So this is going to be optional dot filter In this filter, I'm going to use the same code, whatever 04:50.930 --> 04:51.920 that is here. 04:52.310 --> 04:53.000 Give the logic. 04:53.000 --> 04:59.750 This is going to be 3.5 because Adam is having really poor GPA, not poor. 04:59.750 --> 05:00.680 It's an average GPA. 05:00.980 --> 05:02.720 And then what is the next thing? 05:02.720 --> 05:05.660 The next thing is going to be the map method. 05:05.840 --> 05:11.240 In the map method, we are going to get the student name right. 05:11.240 --> 05:12.800 And what is this going to return? 05:12.800 --> 05:17.470 If you go to the map method, Map method returns an object of type optional. 05:17.480 --> 05:18.280 Right? 05:18.290 --> 05:25.020 Let's go ahead and get that optional of type string, because if you take a look at the student name, 05:25.020 --> 05:27.210 this is of type string. 05:27.960 --> 05:35.940 Now what we can do, we can print this, we print it, it is going to give you the actual value that 05:35.940 --> 05:38.340 it encapsulates. 05:38.340 --> 05:42.180 If you run this example, I didn't call this method it. 05:42.570 --> 05:47.070 So in here, what we are going to do, we are going to call the optional map 05:49.500 --> 05:50.400 optional map. 05:51.660 --> 05:53.730 And then let's go ahead and run this example. 05:53.730 --> 05:58.950 So when you run this example, this is going to call this one and it is going to print the name of the 05:58.950 --> 06:00.960 student, which is nothing but Adam. 06:01.930 --> 06:02.330 There you go. 06:02.350 --> 06:04.030 It printed the value as Adam. 06:04.210 --> 06:06.700 Now let's go ahead and explore the flat method. 06:06.700 --> 06:10.660 I'm thinking of covering this flat method as a next tutorial. 06:10.810 --> 06:16.600 For now, we have covered the filter and map method As part of this tutorial, let's go ahead and explore 06:16.600 --> 06:19.600 the flat flat map in the next tutorial. 06:19.600 --> 06:21.660 With this we came to the end of this tutorial. 06:21.670 --> 06:22.840 Thank you for watching.