WEBVTT 00:00.520 --> 00:01.000 Hi everyone. 00:01.000 --> 00:02.200 Welcome back to this tutorial. 00:02.200 --> 00:08.260 In this tutorial, we'll explore the function interface using that student collection that we have been 00:08.260 --> 00:10.510 using throughout the tutorial. 00:10.510 --> 00:20.560 Now the use cases, we are going to create a map of students and their respective grades meaning and 00:20.560 --> 00:21.940 their respective GPA. 00:23.260 --> 00:23.920 For that purpose. 00:23.920 --> 00:31.450 What I'm going to do, I'm going to create a new class called function student example. 00:32.770 --> 00:34.630 Then I'm going to make this class executable. 00:35.410 --> 00:36.340 SVM. 00:36.790 --> 00:37.630 There you go. 00:37.750 --> 00:39.430 Class is executable now. 00:40.210 --> 00:44.200 The first step is we are going to create the function interface. 00:44.320 --> 00:45.130 Static. 00:46.000 --> 00:47.170 Function interface. 00:48.300 --> 00:50.580 So the input is going to be. 00:52.380 --> 00:59.230 A list of students and the output is going to be a hash map with the student and their GPA. 01:01.610 --> 01:02.900 The list of. 01:03.730 --> 01:05.200 Student is the input. 01:07.080 --> 01:14.520 Followed by that I'm using the option and return to auto import these classes in Mac. 01:15.410 --> 01:18.020 You take a look at the windows, it's alt enter. 01:20.970 --> 01:24.360 And the next thing is it's going to be a map of string. 01:26.220 --> 01:27.090 And double. 01:27.450 --> 01:34.980 The double is a type which is being used to store the student GPAs. 01:35.010 --> 01:36.120 We take a look at it. 01:36.420 --> 01:37.470 The double. 01:39.110 --> 01:40.730 That's what we have been using here. 01:42.180 --> 01:43.050 And then. 01:45.390 --> 01:48.060 For that, let's import the function. 01:48.300 --> 01:49.050 Here you go. 01:49.230 --> 01:49.830 All set? 01:51.020 --> 01:53.060 You're going to name this one as. 01:54.420 --> 01:55.500 Student function. 01:56.770 --> 02:00.100 Now, we all know the input is going to be students, right? 02:00.730 --> 02:01.300 There you go. 02:01.600 --> 02:08.260 And then we are going to open the curly braces because we are going to do a lot of logic in order to 02:08.260 --> 02:09.640 get to that result. 02:09.850 --> 02:13.960 So the lambda body is going to be more than a single line statement. 02:13.960 --> 02:17.710 That's the reason why we have the curly braces open here. 02:18.370 --> 02:19.300 In here. 02:19.300 --> 02:23.770 The first step is we are going to define a map that's going to be string. 02:27.580 --> 02:30.880 And then it is going to be named as student. 02:32.140 --> 02:35.140 Read map equal to new. 02:38.910 --> 02:39.180 Okay. 02:39.330 --> 02:41.100 Now we are going to. 02:41.870 --> 02:47.480 In that shouldn't and using the for each method what we are going to do. 02:48.740 --> 02:51.980 We are going to iterate each and every student. 02:54.200 --> 02:57.590 And then again, open the lambda body. 02:58.190 --> 03:03.350 You're going to populate the student grade map using the put method. 03:03.860 --> 03:07.190 First is going to be to the name. 03:08.220 --> 03:11.640 Followed by that it is going to have student dot get GPA. 03:12.760 --> 03:13.300 There you go. 03:13.420 --> 03:18.490 The map is going to be populated with the student and their appropriate grades. 03:18.910 --> 03:20.710 Now, I'm going to close this. 03:21.430 --> 03:22.800 I have some issues here. 03:22.800 --> 03:23.640 What is that? 03:26.230 --> 03:28.990 This particular map have to return something, right? 03:28.990 --> 03:31.690 This is going to return the student grade map. 03:33.280 --> 03:34.530 Then student grade map. 03:35.560 --> 03:44.260 So now we have implemented the whole functionality and then assign that functionality to this. 03:45.150 --> 03:48.600 Object reference basically to this object. 03:51.510 --> 04:00.720 Now what I'm going to do, I'm going to call the student function dot apply and use a student database 04:00.720 --> 04:04.770 class and get all the students and. 04:05.760 --> 04:09.930 The result is going to be the map of students and their appropriate grades. 04:11.720 --> 04:12.110 There you go. 04:12.350 --> 04:16.400 It printed the value with the students and their appropriate grades. 04:16.430 --> 04:18.920 Now you are changing your mindset. 04:18.920 --> 04:23.410 And then there is a new request came from the business. 04:23.420 --> 04:28.790 Okay, now we want to filter all the students who are greater than. 04:30.130 --> 04:34.000 Grade three level, meaning we go and take a look at the student. 04:34.030 --> 04:35.560 It has a grade level. 04:35.950 --> 04:41.370 They want the students who are the grade of three and four. 04:41.380 --> 04:43.060 So in that case. 04:44.800 --> 04:46.960 You can just change your functionality. 04:47.050 --> 04:52.210 If you take a look at the predicate student example, we have this right and it is defined in static 04:52.210 --> 04:53.080 context. 04:53.080 --> 04:54.610 So I'm going to make use of that. 04:55.070 --> 04:59.590 I'm going to go back to the function student example in here, what I'm going to do. 05:00.900 --> 05:04.050 And apply this logic predicate example Dot. 05:06.450 --> 05:09.300 Believe it is P1 to go to P1. 05:09.540 --> 05:13.260 P1 is the one which has a grade level greater than or equal to three. 05:13.510 --> 05:15.420 Dot test student. 05:17.370 --> 05:24.600 Now, if you take a look at it, we are filtering the student students who are in the grade of three 05:24.600 --> 05:25.100 and four. 05:25.110 --> 05:29.220 Basically, Adam and Emily, they're not going to be printed in the result. 05:31.070 --> 05:31.670 There you go. 05:32.030 --> 05:32.750 Emily is printed. 05:32.750 --> 05:35.840 I believe Emily is part of the third grade only. 05:35.840 --> 05:36.330 Yep. 05:36.350 --> 05:39.020 The result is printed as expected. 05:39.440 --> 05:44.040 So this is the advantage of using lambdas. 05:44.060 --> 05:45.680 So you can plug in. 05:46.840 --> 05:49.330 New features very easily. 05:49.450 --> 05:52.840 And then and it is more readable. 05:53.350 --> 05:58.210 So that's one of the advantage of using Lambda, which have been highlighting from the beginning. 05:59.580 --> 05:59.940 With this. 05:59.940 --> 06:01.740 We came to the end of this tutorial. 06:01.860 --> 06:02.910 Thank you for watching.