WEBVTT 00:00.170 --> 00:00.650 Hi everyone. 00:00.650 --> 00:01.760 Welcome back to this tutorial. 00:01.760 --> 00:07.670 In this tutorial we will code and explore the scenarios where the method reference cannot be used directly, 00:07.670 --> 00:13.130 but refactoring the code will make it eligible to use method reference. 00:14.270 --> 00:14.690 A step. 00:14.690 --> 00:16.430 I'm going to create a class called. 00:17.320 --> 00:19.120 Refactor method. 00:20.060 --> 00:21.680 Reference example. 00:22.560 --> 00:26.940 Want to make this class executable by adding the public static void main method. 00:27.480 --> 00:27.990 There you go. 00:28.860 --> 00:34.410 And for this example, what I'm going to do, I'm going to use one of the Lambda expression which we 00:34.410 --> 00:36.960 had implemented in the prior tutorials. 00:37.050 --> 00:39.710 I'm going to go to this functional interfaces package. 00:39.770 --> 00:45.240 Then I'm going to take this predicate student example, and then I'm going to use this one. 00:46.170 --> 00:51.630 So copy this and then put it here and then discuss about what is this Lambda expression is going to 00:51.630 --> 00:52.140 do. 00:52.410 --> 00:57.360 So it is going to take in a student as an input and then return the Boolean because it is a predicate 00:57.360 --> 00:59.460 functional interface here. 00:59.490 --> 01:04.920 If the grade level of the student is greater than or equal to three, then it is going to return the 01:05.130 --> 01:06.930 boolean value as true. 01:06.930 --> 01:10.770 Otherwise it is going to return the boolean result as false. 01:11.570 --> 01:12.800 Let's test this one. 01:13.690 --> 01:14.950 Want to print the result. 01:14.990 --> 01:17.140 P1 dot test. 01:17.280 --> 01:19.810 So the next thing is we need to pass a student, right? 01:20.020 --> 01:26.050 Let's go and check our database class and then see do we have any utility method that just returns a 01:26.050 --> 01:26.590 student? 01:26.620 --> 01:28.630 No, it doesn't return anything like that. 01:28.660 --> 01:32.890 Let's create a utility method that is going to just return a single student. 01:33.610 --> 01:38.300 What I'm going to do is I'm going to use the supplier function interface for that. 01:38.320 --> 01:44.560 So supplier functional interface is to supply any type that is provided in that context, right? 01:44.650 --> 01:52.150 So I'm going to name this one as a static, and then I'm going to provide a supplier of type student. 01:52.950 --> 01:55.350 Then I'm going to name this one as student supplier. 01:56.350 --> 01:58.180 So let's write the lambda expression. 01:58.180 --> 02:00.250 It doesn't take any input. 02:01.640 --> 02:02.810 And returns a student. 02:02.810 --> 02:07.700 So I'm going to copy one of the student from here and then return that. 02:08.940 --> 02:11.310 And give semicolon here. 02:11.970 --> 02:12.930 What is the issue here? 02:12.930 --> 02:15.510 There is some issue which it is complaining about. 02:16.640 --> 02:17.270 Here. 02:18.290 --> 02:19.190 Missing return statement. 02:19.190 --> 02:21.470 We need to add the return statement. 02:23.330 --> 02:27.380 So a student supplier is ready to supply the students whenever it is invoked. 02:27.380 --> 02:29.750 It is going to supply the student. 02:29.780 --> 02:35.670 So from here, what we are going to do for the test method, we need the student, right? 02:35.690 --> 02:38.780 I'm going to get the student database dot. 02:38.810 --> 02:43.820 So we have one method and another function which is of type lambda. 02:43.820 --> 02:44.170 Right? 02:44.180 --> 02:49.640 So let's use that and then call the get method of that supplier is going to give you the student. 02:50.210 --> 02:50.900 There you go. 02:51.170 --> 02:54.500 And what is the student data that it is returning? 02:54.530 --> 03:01.010 If you take a look at it, the student name is Adam and the grade level is two and the GPAs 3.6. 03:01.010 --> 03:03.500 Gender is male and swimming. 03:03.500 --> 03:06.200 Basketball and volleyball are the list of activities. 03:07.070 --> 03:08.540 Adams part of it. 03:08.810 --> 03:09.560 Now. 03:10.710 --> 03:14.430 Go back to our example and then run this one here. 03:14.430 --> 03:16.110 The grade level is three, right? 03:16.470 --> 03:20.040 Let's try to let's run this and then check what is the result. 03:20.070 --> 03:22.760 It is going to return the result as false. 03:22.770 --> 03:31.710 The reason being the grade level is equal to two for Adam and this condition is evaluated to false. 03:32.840 --> 03:34.580 Now the main use cases. 03:34.610 --> 03:39.170 How can we write a method reference for these kind of implementations? 03:39.650 --> 03:44.930 So basically we need to refactor this code and move this logic into a method. 03:45.020 --> 03:50.390 So what I'm going to do, I'm going to create a method public boolean. 03:52.430 --> 03:53.390 Greater than. 03:54.730 --> 03:55.570 Grade level. 03:56.480 --> 04:02.450 And then what I'm going to do is I'm going to pass the student as an input and have this logic mode 04:02.450 --> 04:04.190 inside this. 04:05.590 --> 04:09.630 That and this needs to have the return keyword. 04:09.720 --> 04:13.260 And this logic is successfully moved inside this method. 04:13.290 --> 04:14.550 The next step is. 04:16.070 --> 04:23.000 Let's give the class name refactor method, reference example, and then give the greater than grade 04:23.000 --> 04:23.480 level. 04:24.320 --> 04:26.180 Let's see what it is complaining. 04:26.330 --> 04:32.270 So we have to make that one static because we are trying to reference a method in the static context. 04:32.300 --> 04:34.860 Let me run this and then check the result. 04:34.880 --> 04:37.520 It should give me the false as a result. 04:38.030 --> 04:39.670 We have the result as expected. 04:39.680 --> 04:44.810 So we have successfully refactor the code which was not compatible for method reference. 04:45.050 --> 04:47.420 And one more thing to call out here. 04:47.420 --> 04:52.100 It is not mandatory that each and every code should be compatible with the method. 04:52.100 --> 04:58.820 Reference syntax is not possible to write every code to be method reference compatible in a real world 04:58.820 --> 04:59.820 application. 04:59.840 --> 05:06.920 I just showed here a pattern on how to make a code compatible for method reference syntax. 05:06.950 --> 05:08.960 With this we came to the end of this tutorial.