WEBVTT 00:00.570 --> 00:01.110 Hi everyone. 00:01.110 --> 00:02.400 Welcome back to this tutorial. 00:02.400 --> 00:08.250 In this tutorial, we will explore the group by which accepts two parameter as an input in the previous 00:08.250 --> 00:08.670 tutorial. 00:08.670 --> 00:12.810 If you take a look at it, we just passed the one parameter version. 00:12.810 --> 00:17.010 We are going to explore the two parameter version in this tutorial. 00:21.470 --> 00:27.680 The first use case that we are going to code, we are going to create a two level grouping. 00:28.890 --> 00:33.420 Going to create a method called public static void. 00:35.180 --> 00:35.660 Level. 00:37.010 --> 00:43.010 Grouping, and then I'm going to give it as one because we'll be coding multiple examples on the same 00:43.040 --> 00:46.160 two level, on the same two parameter version of grouping. 00:46.160 --> 00:46.500 Why? 00:47.760 --> 00:53.730 So I'm going to call the get all students and then the next call is going to be stream and the next 00:53.730 --> 00:55.010 call is going to be collect. 00:55.020 --> 01:01.380 So we want to collect or we want to group the students based on their grade level. 01:01.380 --> 01:06.150 So it's going to be student colon, colon grade level. 01:06.150 --> 01:11.760 So this is the classifier for this we have to give the grouping by. 01:13.000 --> 01:14.020 Let's close it here. 01:14.590 --> 01:20.320 So this is similar to the previous version that we have here in here, what we are going to do, we 01:20.320 --> 01:23.440 are going to add the second parameter. 01:23.440 --> 01:28.120 If you go ahead and take a look at the grouping by it, accept it, accept the first parameter, which 01:28.120 --> 01:31.510 is a classifier, and the second parameter which is a downstream. 01:31.510 --> 01:38.200 So this downstream can be any type of grouping by implementation or any type of collector implementation. 01:38.200 --> 01:44.560 Basically what I'm going to do again in this example, I'm going to do another grouping by basically 01:44.560 --> 01:45.070 what it is. 01:45.100 --> 01:52.240 What is this going to happen is that this is going to create another level of map. 01:52.240 --> 01:58.270 So here we have the map and the value values or list of students. 01:58.270 --> 02:02.020 But in this use case, it is going to be a map of string. 02:02.020 --> 02:04.030 And again, another map here. 02:04.030 --> 02:10.540 So in here, what we are going to do, I'm going to group the students with this same category. 02:11.830 --> 02:12.760 There you go. 02:12.760 --> 02:15.160 So let's take a look at the output. 02:15.430 --> 02:21.010 It's going to be map of string, which is going to hold the grade level. 02:21.010 --> 02:26.080 And then the values are again, going to be map of string. 02:27.010 --> 02:29.470 And list of student. 02:32.250 --> 02:33.970 So this is called. 02:35.590 --> 02:36.640 Global mapping. 02:40.220 --> 02:43.070 So this is called two level mapping. 02:43.700 --> 02:44.000 Let's see. 02:44.000 --> 02:45.200 There are some issues here. 02:45.200 --> 02:46.760 Let's go ahead and take a look at it. 02:46.940 --> 02:49.210 This is going to be a student map. 02:49.220 --> 02:51.650 This is good here in here. 02:51.650 --> 02:52.880 What is going on? 02:53.450 --> 02:55.400 Let's give the name as student map. 02:56.370 --> 02:59.880 The map of it would be a string. 02:59.880 --> 03:02.540 Let's go and check what is a grade level or the grade level is. 03:02.550 --> 03:05.610 And so in that case it is going to be integer. 03:06.580 --> 03:07.150 There you go. 03:07.150 --> 03:09.520 So let's revisit this example again. 03:09.520 --> 03:12.820 So in this example, we are performing two level grouping. 03:12.820 --> 03:18.280 The first grouping is at the grade level and the second grouping is again going to be similar to the 03:18.280 --> 03:19.750 one which we coded here. 03:19.750 --> 03:26.050 It is going to tag each and every student as outstanding or average based on their GPA. 03:26.740 --> 03:28.300 Let's go ahead and run this example. 03:28.300 --> 03:34.030 Once you look at the result it will make it will give you more idea or more understanding of what's 03:34.030 --> 03:34.990 going on here. 03:38.810 --> 03:40.430 I'm going to run this example. 03:43.660 --> 03:45.310 And we are not printing anything here. 03:45.310 --> 03:47.580 That's the reason why we don't see anything here. 03:47.590 --> 03:48.970 I'm going to print it here. 03:50.830 --> 03:52.390 Run this example again. 03:52.720 --> 03:53.590 There you go. 03:53.590 --> 03:55.120 You have the result here. 03:55.120 --> 03:56.850 Let's let's review the result here. 03:56.860 --> 04:05.260 So here it has the first level of map, which has a key as a grade level and the second level of map, 04:05.260 --> 04:11.650 which is tagging each and every student in each and every grade as average and outstanding. 04:11.650 --> 04:16.900 If you take a look at it in the second grade, there is one average student who is Adam and there is 04:16.900 --> 04:18.640 one outstanding student who is Jenny. 04:19.300 --> 04:22.720 That's the same case with the third grade and fourth grade. 04:22.720 --> 04:32.560 In the fourth grade, there is no average student because their GPA is 4.0 and 3.9, which is matching 04:32.560 --> 04:34.450 the outstanding key. 04:36.000 --> 04:39.000 Let's explore one more example on this same topic. 04:39.000 --> 04:41.310 So here we have used grouping by rate. 04:41.340 --> 04:43.110 We can also use. 04:44.480 --> 04:45.620 Some other. 04:45.740 --> 04:48.200 I just copied the method from there and put it here. 04:48.230 --> 04:50.690 Let's use some other collector here. 04:50.720 --> 04:53.030 The collector is going to be. 04:55.000 --> 04:55.930 Summing int. 04:55.960 --> 05:00.130 So summing int is one collector which we have explored in one of the previous tutorial. 05:00.340 --> 05:02.230 I'm going to use the summing int. 05:02.260 --> 05:08.800 What it is going to accept is that it is going to take student colon colon notebooks. 05:09.370 --> 05:11.680 So here it is going to be. 05:13.190 --> 05:15.320 A map of integer. 05:16.550 --> 05:18.290 An integer, right? 05:18.290 --> 05:25.580 Because this summing int is again going to return an integer and this grade level is already mapping 05:25.610 --> 05:26.450 to an integer. 05:26.450 --> 05:33.350 So this is another way of using the two parameter grouping by. 05:34.270 --> 05:34.710 Method. 05:34.720 --> 05:40.720 So the first one is a classifier, which is going to be the key for the total. 05:40.900 --> 05:41.920 Output map. 05:41.920 --> 05:46.300 And then this determines what is a value that it is going to have. 05:46.330 --> 05:48.220 Let's call this method and check the result. 05:50.800 --> 05:51.960 Want to take a look at it. 05:53.120 --> 05:54.020 I'm going to run this. 05:55.430 --> 05:55.660 Run. 05:55.660 --> 05:56.320 The result? 05:56.350 --> 05:59.740 The two has 23 and three. 05:59.770 --> 06:04.540 Third grade has 19 books and fourth grade has 29 books. 06:05.520 --> 06:11.610 And if you want to group them based on based on their name, you can do that too. 06:11.660 --> 06:16.320 If we do, a get name is going to give you the key as. 06:17.750 --> 06:22.000 Thus because it's going to be a string, because getName is of type string, right? 06:22.010 --> 06:27.080 If I run this example, it is going to have name and their appropriate notebooks count. 06:27.110 --> 06:27.840 There you go. 06:27.860 --> 06:29.270 Adam as a notebook. 06:29.420 --> 06:30.630 Adam as 11 notebooks. 06:30.650 --> 06:31.850 Emily has ten. 06:32.030 --> 06:38.270 The following students have their appropriate notebook count mapped here, and it is grouped as a map 06:38.300 --> 06:38.810 here. 06:39.020 --> 06:42.770 So this is all about the two parameter grouping by. 06:43.750 --> 06:44.080 With this. 06:44.080 --> 06:45.710 We came to the end of this tutorial. 06:45.730 --> 06:46.930 Thank you for watching.