WEBVTT 00:01.040 --> 00:01.640 Hi everyone. 00:01.640 --> 00:02.980 Welcome back to this tutorial. 00:02.990 --> 00:07.130 This is a part two of the reduce function. 00:07.130 --> 00:12.200 Now I'm going to build a use case exploring the reduce function. 00:12.200 --> 00:20.000 We are going to leverage the student database and then we are going to find out how to reduce the student 00:20.030 --> 00:24.830 who has the highest GPA in this whole collection that we have. 00:24.950 --> 00:30.140 So I'm going to create a method called public static. 00:31.390 --> 00:33.070 Optional of student. 00:35.990 --> 00:38.630 So this is going to give you get the. 00:40.080 --> 00:41.670 Highest GPA. 00:47.160 --> 00:48.150 For this. 00:48.660 --> 00:51.870 I'm going to put this in presentation mode so the code will be clear. 00:54.430 --> 00:55.210 Mission mode. 00:55.360 --> 00:59.110 So in here, what we are going to do, the first step is we are going to. 01:00.180 --> 01:06.690 All the student database dot, get all students, go back to that method and then see. 01:07.260 --> 01:13.410 So these are the six students we have as part of this collection in here, the highest grade student 01:13.410 --> 01:15.690 out of all, the highest GPA student. 01:15.690 --> 01:21.390 Out of all these six students is Emily, who has a GPA of 4.0. 01:21.480 --> 01:30.330 Our goal is to how to get to that value and how to return that using the reduce operation or reduce 01:30.330 --> 01:31.020 function. 01:33.370 --> 01:40.690 So the first step is we are going to create the stream and then we are going to use the reduce method. 01:41.320 --> 01:48.730 This method is going to take in two input because it is a binary operator, as you see. 01:48.850 --> 01:53.770 And then I'm going to assign two values S1 and S2. 01:54.370 --> 02:01.660 These are the student one and student two And what we are going to do is that we're going to compare. 02:03.870 --> 02:06.610 S1 dot get GPA. 02:08.620 --> 02:15.210 I'm going to open a remove this, open the curly braces and close the curly braces. 02:16.690 --> 02:17.320 If the. 02:21.090 --> 02:22.350 S1 dot. 02:25.980 --> 02:26.460 EPA. 02:29.670 --> 02:30.600 Don't need this, Right. 02:30.600 --> 02:32.640 So you don't need this here. 02:33.840 --> 02:38.730 Impression dot get GPA is greater than S2. 02:38.760 --> 02:40.080 Dot get GPA. 02:42.820 --> 02:45.280 Then return as one. 02:46.780 --> 02:47.470 Else. 02:52.870 --> 02:58.420 So this is the functionality which is going to give us the desired result. 02:58.450 --> 03:03.760 What I'm going to do, if you take a look at it, it is returning an optional because I do not have 03:03.760 --> 03:05.270 any default value here. 03:05.290 --> 03:07.730 I want I don't want to pass any default value. 03:07.750 --> 03:11.590 I'm just expecting the result as a optional student. 03:11.770 --> 03:13.840 So I'm going to go back here. 03:14.990 --> 03:16.310 And I'm going to call. 03:17.040 --> 03:20.690 I don't have to pass any inputs because this method has a call. 03:22.070 --> 03:24.500 You get all the students, I'm going to return this. 03:25.760 --> 03:30.980 So in here is going to be optional of student. 03:32.220 --> 03:35.460 And then this is going to be student optional. 03:37.070 --> 03:38.450 If I do. 03:39.710 --> 03:41.000 God is present. 03:42.060 --> 03:47.880 And then I'll perform the student optional dot get. 03:49.590 --> 03:50.520 Run this example. 03:50.520 --> 03:53.190 It is going to give me Emily as a result. 03:53.190 --> 03:56.340 As you see, it gave me Emily as a result. 03:56.620 --> 03:58.590 So how is this determining the result? 03:58.590 --> 04:00.780 That might be the question which is running in your mind. 04:00.810 --> 04:05.520 So the reduce operation is going to get the students one by one, right? 04:06.150 --> 04:08.400 Students one by one. 04:08.610 --> 04:11.490 So it is here we have the condition. 04:11.490 --> 04:18.780 This condition is a one which is a key factor here that determines which student has the highest GPA. 04:19.050 --> 04:24.690 And then it compares that with each and every value that is being parsed out of the stream. 04:24.690 --> 04:31.620 And then it maintains the highest, the student with the highest grade, and that student will be returned 04:31.620 --> 04:33.330 towards the end. 04:35.100 --> 04:36.770 That's what is happening behind the scenes. 04:36.780 --> 04:40.100 So this logic looks more clumsy to me. 04:40.110 --> 04:43.650 How can we rewrite it in such a way that it looks more readable? 04:43.910 --> 04:44.970 So I'm gonna. 04:46.370 --> 04:46.690 Does. 04:47.090 --> 04:56.690 What I'm going to do is I'm going to do S1 dot get GPA is greater than S2 dot get GPA. 04:57.520 --> 05:00.950 So I'm going to use a ternary operator question mark. 05:01.860 --> 05:02.520 As one. 05:03.550 --> 05:03.970 Are. 05:05.530 --> 05:06.980 This looks more readable. 05:07.000 --> 05:08.920 Let's run this and then check. 05:09.400 --> 05:11.260 Is it returning the same result? 05:12.040 --> 05:12.600 There you go. 05:12.610 --> 05:14.020 It returned the same result. 05:14.800 --> 05:21.130 So this is one of the use case which is very popular while using the reduce function. 05:21.160 --> 05:29.680 The reduce functions idea is to get the stream and then try to reduce that stream to one single value 05:29.680 --> 05:31.060 that you are looking for. 05:32.620 --> 05:35.440 But thus we came to the end of this tutorial. 05:35.800 --> 05:36.970 Thank you for watching.