WEBVTT 00:00.510 --> 00:01.020 Hi everyone. 00:01.020 --> 00:02.310 Welcome back to this tutorial. 00:02.310 --> 00:08.580 In this tutorial we will discuss about the local variables and its restrictions with Lambda expressions. 00:09.470 --> 00:11.180 What are local variables? 00:11.300 --> 00:16.640 You might know what is a local variable already, but I would like to throw some light on this. 00:16.670 --> 00:22.550 Any variable that is declared inside a method is called a local variable. 00:22.970 --> 00:27.230 Lambda have some restrictions on using the local variables. 00:27.260 --> 00:29.540 To summarize, there are two restrictions. 00:29.570 --> 00:37.370 Number one, you are not allowed to use the same local variable name as a lambda parameter or inside 00:37.370 --> 00:38.510 the lambda body. 00:38.540 --> 00:46.310 Number two, you are not allowed to reassign a new value to a local variable in the lambda expression. 00:46.340 --> 00:49.700 One other thing is that there are no restrictions. 00:49.700 --> 00:53.530 For instance, variables in lambda expression. 00:53.540 --> 01:01.070 What does it mean is that you are allowed to modify or change a value of the instance variable. 01:01.100 --> 01:05.120 Let's understand this by coding some examples. 01:06.760 --> 01:09.760 Let me open IntelliJ and code this examples. 01:10.980 --> 01:11.420 There you go. 01:11.430 --> 01:12.270 I have the intelligence. 01:12.300 --> 01:12.690 Open. 01:12.690 --> 01:16.230 The first step is I'm going to create a class specific for this one. 01:16.440 --> 01:20.280 I'm going to name this one as a lambda variable one. 01:20.820 --> 01:25.500 Let me make this class executable by adding the public static void main method. 01:25.530 --> 01:32.850 The first restriction is that you're not allowed to use the local variable name in the lambda expression 01:32.850 --> 01:33.720 or body. 01:35.170 --> 01:38.870 Why not declare a local variable called int I equal to zero? 01:39.630 --> 01:42.060 Okay, I'm going to code a simple use case here. 01:42.080 --> 01:45.830 Basically consumer which takes in an integer. 01:46.520 --> 01:51.770 I'm going to name this one as C1 equal to let's import this consumer. 01:51.800 --> 01:52.310 There we go. 01:52.340 --> 01:53.870 The consumer is imported. 01:53.900 --> 02:00.950 What I'm going to do is I'm going to pass in I, I'm going to try to pass the I and then try to print 02:00.950 --> 02:01.730 this value. 02:07.320 --> 02:12.300 So if we take a look at it here, it has the compilation issue variable. 02:12.300 --> 02:15.180 I is already defined in this scope. 02:15.300 --> 02:17.010 So this is one of the restriction. 02:17.010 --> 02:23.550 You are not allowed to use the same variable which is already defined in this method scope. 02:23.550 --> 02:25.140 Here the method is main method. 02:25.170 --> 02:27.930 If I give this one as I1, then that is fine. 02:28.320 --> 02:30.630 Let's talk about the next restriction. 02:30.630 --> 02:33.510 So there is a local variable called int I equal to zero. 02:33.510 --> 02:40.920 If you try to declare the same variable like int i equal to two, this is not allowed because you have 02:40.920 --> 02:44.820 a local variable already defined in this method scope. 02:46.310 --> 02:47.660 There is a first restriction. 02:47.660 --> 02:53.480 Let's talk about the next restriction, which is trying to reassign a variable. 02:54.910 --> 02:55.960 The new value. 02:56.830 --> 02:58.870 So I'm going to create a class called. 03:00.160 --> 03:02.950 Lambda variable to. 03:05.630 --> 03:07.820 And then let's make this class executable. 03:09.380 --> 03:15.080 So what I'm going to do is I'm going to declare a variable called int value equal to four. 03:15.110 --> 03:18.470 So this is the local variable, right? 03:18.470 --> 03:22.340 And the next step is I'm going to declare a consumer interface. 03:23.240 --> 03:27.050 Of type integer and the name that one as C1. 03:27.560 --> 03:29.960 Let's import this consumer interface. 03:30.270 --> 03:33.320 Then I'm going to pass a value called I. 03:35.290 --> 03:40.450 So in here, what we are going to do, we are going to print the value of four. 03:42.980 --> 03:43.550 Right. 03:43.580 --> 03:47.480 No issues until this point or you can print the value of. 03:49.080 --> 03:50.850 The local variable value. 03:51.210 --> 03:56.700 So I'm going to call this 17. accept and pass the value as four. 03:56.880 --> 04:00.240 So this is going to perform some summation of. 04:01.180 --> 04:02.980 Value plus I and print the value. 04:03.020 --> 04:07.120 So if I run this one, it is going to print the value as eight. 04:07.270 --> 04:11.290 Now let's say you want to perform some operation on this one. 04:11.290 --> 04:14.740 Let's say you want to reassign the value like this. 04:14.740 --> 04:18.220 You want to increment the value whenever you call it here. 04:19.180 --> 04:21.060 There is a error, right? 04:21.070 --> 04:27.360 We got an error variable used in lambda expression should be final or effectively final. 04:27.370 --> 04:34.150 What does it mean is that this is a second restriction so you are not allowed to modify any value, 04:34.510 --> 04:39.730 meaning modify any local variable that is being referenced in the lambda scope. 04:39.850 --> 04:44.080 Let's say you want to change this value value equal to six. 04:44.110 --> 04:45.580 Even then, this is not allowed. 04:45.580 --> 04:50.050 Even though you are not modifying this value inside the lambda scope. 04:50.050 --> 04:54.130 Still, you are trying to modify this inside the method scope, right? 04:54.550 --> 04:56.080 That is also not allowed. 04:56.110 --> 05:01.300 Let's say you are going to move this one as an instance variable. 05:01.300 --> 05:04.510 I'm going to copy this line and then move it over here. 05:06.560 --> 05:11.450 And then I'm going to have this one increment the value. 05:11.480 --> 05:12.610 So what is the error? 05:12.620 --> 05:18.050 Create field value or make me non-static or make value static? 05:18.050 --> 05:21.440 So we are trying to access the value in the static context. 05:21.440 --> 05:26.150 That's the reason why you have to define it as a define it with a static keyword. 05:26.150 --> 05:30.290 So in here this is earns, this is an instance variable. 05:30.950 --> 05:32.930 In that case, there are no issues. 05:32.930 --> 05:38.630 So as I mentioned before in the presentation itself, for instance, variables or class variables, 05:38.630 --> 05:39.800 there are no restrictions. 05:39.800 --> 05:48.020 You are allowed to reassign or change or modify the value, but for local variables you are not allowed 05:48.020 --> 05:48.590 to do that. 05:48.590 --> 05:50.540 Let's run this example and then check. 05:50.630 --> 05:51.590 There you go. 05:51.590 --> 05:54.800 It incremented the value from 4 to 5. 05:54.830 --> 05:57.830 That's the reason why you see the result as nine. 06:00.480 --> 06:00.810 With this. 06:00.810 --> 06:02.480 We came to the end of this tutorial. 06:02.490 --> 06:07.830 Let's take a look at another concept called Effectively Final in the next tutorial. 06:08.070 --> 06:09.300 Thank you for watching.