WEBVTT 0 00:00.180 --> 00:05.430 Hi Everyone will go back to this tutorial. In this tutorial will implement the comparator interface using 1 00:05.430 --> 00:06.320 Lambda. 2 00:06.750 --> 00:17.280 Let's go ahead and code this one. First step is that I'm going to create a class called ComparatorLambdaExample. 3 00:19.050 --> 00:24.720 And then I'm going to make this class executable. The way to make this class executable is by adding 4 00:24.740 --> 00:27.330 the public static void main(). There you go! 5 00:27.330 --> 00:30.750 We have the class ready to run. 6 00:30.930 --> 00:32.730 Before we code this one let's check 7 00:32.730 --> 00:38.820 what is the abstract method the comparator class has and what is the purpose it ? I am going to press the shift 8 00:38.820 --> 00:39.540 key twice. 9 00:39.570 --> 00:41.930 It is giving me this window search everywhere. 10 00:42.160 --> 00:45.870 Then I'm going to search for Comparator. Search for Comparator 11 00:45.870 --> 00:51.000 I have a lot of different classes here the one which I'm going to take a look at is the one which has which 12 00:51.000 --> 00:56.940 is having the icon as "I" stands for interface . Because that is the one which we are going to implement 13 00:56.940 --> 00:57.370 now. 14 00:57.920 --> 00:59.120 Select this one. 15 01:03.190 --> 01:03.660 OK. 16 01:03.800 --> 01:08.210 If you take a look at it it has this @FunctionalInterface 17 01:08.830 --> 01:11.500 annotation meaning this is a Function Interface. 18 01:11.660 --> 01:19.230 The next step in the process is that if you take a look at it it is available in Java 19 01:19.230 --> 01:25.680 JDK since 1.2. And what is abstract method that it has ? 20 01:25.680 --> 01:28.040 It has the method called compare(). 21 01:28.140 --> 01:32.330 And the purpose of that one is to compare two inputs of any type. 22 01:32.360 --> 01:39.900 Could be Integer, Double , Float, String or etc., and the idea is to write your own logic on how 23 01:40.140 --> 01:43.740 you want to compare the inputs in your implementation. 24 01:43.820 --> 01:48.320 Lets scroll down a bit and check what are the different things that this interface has. 25 01:48.330 --> 01:51.950 There are some other method with the default keyword. 26 01:52.170 --> 01:57.200 You might be wondering that the definition of functional interface is just to have one abstract method. 27 01:57.220 --> 01:59.470 But I see other methods too here. 28 01:59.490 --> 02:02.910 Is it not breaking the contract of a Functional Interface? 29 02:02.910 --> 02:04.300 The answer is No. 30 02:04.710 --> 02:10.980 default() methods are something which got introduced as part of Java 1.8 . I'll be covering this topic as 31 02:10.980 --> 02:12.900 a separate section in this course. 32 02:12.930 --> 02:15.280 Now let's not worry about the default keyword. 33 02:15.300 --> 02:19.530 Let's go ahead and implement this Comparator interface. 34 02:19.540 --> 02:26.480 Lets write the code in implementing the Comparator interface the prior Java 8 way and then the lambda approach. 35 02:26.630 --> 02:29.860 Let me give some comment here prior Java 8. 36 02:30.250 --> 02:33.830 And then give Comparator. 37 02:34.200 --> 02:38.200 I'm going to compare two Integers part of this Comparator. 38 02:38.690 --> 02:45.900 Let me give a name and then the prior java is by creating the anonymous classes. 39 02:45.980 --> 02:52.540 Create Comparator instance. There you go ! The Comparator's compare method is here. Now we will write the logic 40 02:52.540 --> 02:53.220 in here. 41 02:53.300 --> 03:00.470 What I am going to do is I'm going to compare I am going to use the compareTo() method which 42 03:00.470 --> 03:01.620 is part of the Integer. 43 03:02.060 --> 03:06.290 Lets write the logic in here. 44 03:06.360 --> 03:16.580 If both the values are the same then it is going to return zero which is o1 == o2 45 03:16.580 --> 03:22.770 o1 == o2; 46 03:22.780 --> 03:37.610 Next step is if o1 > o2 then it is going to return 1. Next is -1 47 03:37.710 --> 03:44.110 If o1 < o2. This is what this compareTo() 48 03:44.110 --> 03:46.020 is going to do. 49 03:46.090 --> 03:53.920 Now let's call this anonymous class implementation. How do we do it ? Am gonna have 50 03:54.480 --> 03:57.710 Result of the comparator is 51 04:02.460 --> 04:05.510 here we are going to print the result. 52 04:05.660 --> 04:12.530 I'm going to call comparator and it is going to give the recommendation of compare(). What is the input that 53 04:12.530 --> 04:16.770 we're going to pass ? I'm going to pass (3,2). Lets run this! 54 04:20.080 --> 04:22.020 So the result of the comparator is 1. 55 04:22.020 --> 04:25.510 Until now there is nothing new here. 56 04:25.580 --> 04:32.440 It's just the old way. Most of the developers who have worked using Comparator they would have 57 04:32.450 --> 04:44.510 Implemented it this way. Now lets implement it using the Lambda way. Comparator and 58 04:44.630 --> 04:49.570 am going to give it a name called comparatorLambda = () 59 04:49.630 --> 04:59.600 If you take a look at the Comparator interface it accepts two inputs, I am going to pass those (Integer a, Integer b) 60 05:00.390 --> 05:05.970 (Integer a, Integer b) -> followed by that lets put in the arrow. The syntax for 61 05:06.040 --> 05:09.260 the lambda body is by giving the curly braces. 62 05:09.300 --> 05:18.040 Right. Now what we will do we will do a.compareTo(b) 63 05:21.430 --> 05:25.730 But there is some compilation issue! I think the result is have to return this right ? 64 05:30.680 --> 05:34.530 Lets take a look at the issues that we're facing here is expecting this ";" correct. 65 05:37.800 --> 05:40.010 Ideally if you take a look at it 66 05:40.370 --> 05:43.020 it is just single statement right ? 67 05:43.140 --> 05:45.990 If you remember from the previous tutorial. If it is a single statement 68 05:46.020 --> 05:47.450 we don't even need this. 69 05:52.010 --> 05:52.580 Thats it! 70 05:52.790 --> 06:02.650 So now we have implemented comparator interface using Lambda. Am gonna call this one by copying the same. 71 06:02.660 --> 06:14.860 "Result of the Comparator using Lambda is :" In here we are going to use the comparator. Lets run this. 72 06:17.520 --> 06:20.470 So we have successfully implemented it. The results 73 06:20.540 --> 06:26.420 if you take a look at it both are the same and we have successfully implemented the Comparator interface 74 06:26.450 --> 06:27.740 using lambda. 75 06:27.760 --> 06:32.430 Next up is here we are explicitly mentioning the type. 76 06:32.450 --> 06:36.880 Ideally you don't have to do it because here you have already mentioned that type. 77 06:37.040 --> 06:41.830 that this particular lambda expression or this Comparator interface is going accept. 78 06:41.900 --> 06:47.110 So in those kind of scenarios we don't even have to provide the type explicitly there. 79 06:47.120 --> 06:55.890 I'm going to name this one as comparatorLambda1. Lambda is really really smart enough to know to 80 06:56.270 --> 07:01.040 type cast this input to integer. 81 07:01.070 --> 07:06.460 So, I'm gonna run this. 82 07:06.690 --> 07:12.760 And then I am going to use the comparatorlambda1 instance and run this. 83 07:15.540 --> 07:23.300 Result is 1. As part of the tutorial we have explored the lambda expression that accepts 84 07:23.390 --> 07:26.270 an input and returns an output. 85 07:26.560 --> 07:34.430 Advantages are clearly evident if you compared this syntax with this syntax. Lambda lets you write more concise 86 07:34.520 --> 07:36.080 and clear code. 87 07:36.140 --> 07:39.800 It might be difficult to adapt in the beginning, 88 07:39.800 --> 07:47.820 once you get the hang of the lambda expression. You will love it! I will cover more about Lambdas and its advantages in 89 07:47.950 --> 07:49.760 the upcoming tutorials. 90 07:49.840 --> 07:51.910 With this we came to the end of the territorial. 91 07:52.070 --> 07:52.940 Thank you for watching.