WEBVTT 00:00.320 --> 00:00.890 Hi everyone. 00:00.890 --> 00:02.180 Welcome back to this tutorial. 00:02.180 --> 00:07.260 In this tutorial we will code and explore the by function functional interface. 00:07.280 --> 00:12.470 The first step is I'm going to search for that by function function interface and then see what is that 00:12.470 --> 00:13.280 all about. 00:16.160 --> 00:21.200 So by function, functional interface is similar to the function interface, but the only difference 00:21.200 --> 00:24.950 is the by function accepts two inputs and then produces one output. 00:25.100 --> 00:28.760 I'm going to open the function functional interface two and then compare these two. 00:31.090 --> 00:36.100 So if we take a look at the function, it has a play method as like the by function method, but it 00:36.100 --> 00:39.010 accepts only one input and one output. 00:39.630 --> 00:45.870 And it has a compost method and another method and it has a static identity method. 00:46.110 --> 00:49.830 But the by function method doesn't have all those methods. 00:49.830 --> 00:51.840 It just has the and then method. 00:52.680 --> 00:54.570 Now let's go ahead and code this. 00:55.550 --> 00:58.700 Scenario using the by function functional interface. 00:59.180 --> 01:01.250 I'm going to create a class called. 01:02.090 --> 01:03.050 By function. 01:04.580 --> 01:05.180 Example. 01:06.900 --> 01:11.790 And then I'm going to make this class executable by adding the public static void main method. 01:11.880 --> 01:17.160 The use case that we are going to code is that my function is going to accept two inputs, right? 01:17.190 --> 01:19.020 First one is going to be the list of students. 01:19.020 --> 01:23.160 The second one we are going to pass a predicate as an input. 01:23.160 --> 01:29.100 So until now, we have never passed a functional interface implementation as an input. 01:29.190 --> 01:35.190 In this example, we are going to explore that and the output is going to be a map of students and their 01:35.190 --> 01:36.930 respective GPAs. 01:37.350 --> 01:42.390 Let's create the instance of by function function, interface by function. 01:42.390 --> 01:44.280 So it is going to take three. 01:45.440 --> 01:50.030 Parameters passed to are going to be the input and third one is going to be the output. 01:50.240 --> 01:52.940 The first one is going to be the list of students. 01:54.500 --> 01:56.240 Riggo Coldset. 01:56.240 --> 01:58.220 And the next one is going to be. 01:59.060 --> 02:01.190 Predicate of student. 02:03.760 --> 02:09.970 So this is the functional interface which we are passing as an input to that by function functional 02:09.970 --> 02:10.510 interface. 02:11.640 --> 02:15.900 Predicate of student hours typo here. 02:16.620 --> 02:17.790 Let's import predicate. 02:18.850 --> 02:19.960 The third one is the output. 02:19.990 --> 02:20.650 What is the input? 02:20.680 --> 02:21.560 We are output. 02:21.580 --> 02:23.710 The output is going to be map of. 02:24.820 --> 02:31.870 Ring and double basically map of the names, which is of type string and their respective GPUs. 02:31.900 --> 02:32.920 GPUs are in. 02:36.400 --> 02:38.890 And I'm going to give a name by function. 02:39.640 --> 02:41.560 So this is going to accept. 02:43.090 --> 02:46.000 The shouldn't list, which is equivalent to students. 02:47.050 --> 02:51.130 And then is going to perform some operation. 02:51.490 --> 02:54.310 The first step is we are going to initialize. 02:55.950 --> 02:57.090 String double. 02:57.090 --> 02:59.730 We are going to create a HashMap. 03:02.960 --> 03:08.660 Student grade map equal to new hash map. 03:11.200 --> 03:11.500 It. 03:11.860 --> 03:12.570 What is the next step? 03:12.580 --> 03:16.540 The next step is we are going to iterate the student list. 03:17.970 --> 03:18.600 Reach. 03:21.760 --> 03:23.680 And we are going to use. 03:24.870 --> 03:25.710 This predicate. 03:26.620 --> 03:28.990 Right if shouldn't predicate. 03:30.310 --> 03:32.380 Dot test student. 03:34.010 --> 03:39.020 Then add those student in the student grade map dot put. 03:39.780 --> 03:44.550 Didn't dot get name comma didn't dot get. 03:46.870 --> 03:49.180 And then we have to return this hash map. 03:49.540 --> 03:53.020 The next thing, return the student grade map. 03:54.640 --> 03:56.110 Not a semicolon here. 03:56.590 --> 03:57.100 There you go. 03:57.100 --> 04:00.790 We have the by function functional interface implementation ready. 04:00.820 --> 04:03.850 The next step is we are going to pass some input to it. 04:04.240 --> 04:08.050 So let's create the System.out.println. 04:09.630 --> 04:10.080 In here. 04:10.080 --> 04:14.400 What we are going to do, we are going to do by function dot apply. 04:14.430 --> 04:15.180 We take a look at it. 04:15.180 --> 04:17.050 It takes two input parameters. 04:17.080 --> 04:19.440 So using the student database class. 04:21.710 --> 04:26.670 Database, you're going to get all the list of students and then we have to pass a predicate. 04:26.690 --> 04:28.310 Let's go and check this predicate. 04:28.310 --> 04:29.270 Student example. 04:29.600 --> 04:35.180 I'm going to use this predicate in order to filter the. 04:37.540 --> 04:38.340 Students. 04:38.350 --> 04:41.590 So I'm going to use predicate example. 04:44.600 --> 04:45.270 Pterygoids. 04:45.470 --> 04:48.200 F stands for Functional interface. 04:48.230 --> 04:49.340 We're going to use P1. 04:49.580 --> 04:50.060 Basically. 04:50.060 --> 04:51.470 What is that it is going to do? 04:51.470 --> 04:55.080 It is going to filter the students based on their grade level. 04:55.100 --> 05:02.060 So it is going to produce the output with all the students who are the grade level greater than or equal 05:02.060 --> 05:02.690 to three. 05:03.900 --> 05:05.310 Then I'm going to run this example. 05:08.840 --> 05:09.350 There you go. 05:09.380 --> 05:14.450 It gave all the students whose grade level is greater than or equal to three. 05:14.450 --> 05:20.450 Let's say you change your mind and then you want to use this another functional interface predicate 05:20.540 --> 05:26.510 implementation, which has this filter which is equivalent to the GPA greater than or equal to 3.9. 05:26.960 --> 05:28.040 I'm going to run this. 05:29.200 --> 05:30.980 Is going to produce a result accordingly. 05:31.160 --> 05:38.420 Now it is only three results in the output because only three results from this election matches the 05:38.420 --> 05:39.110 filter. 05:39.110 --> 05:45.620 Basically, who are having the grade, which is the GPA greater than or equal to 3.9. 05:47.790 --> 05:48.120 With this. 05:48.120 --> 05:49.810 We came to the end of this tutorial. 05:49.830 --> 05:50.910 Thank you for watching.