WEBVTT 0 00:00.440 --> 00:05.440 Hi everyone welcome come back to the tutorial. In this tutorial we're going to code another example to 1 00:05.440 --> 00:11.560 showcase the difference between the imperative style of programming and declarative style of programming. 2 00:11.800 --> 00:16.350 The use case is to remove the duplicates from a list of integers. 3 00:16.360 --> 00:19.830 Let's code this one. I have the IntelliJ open. 4 00:19.950 --> 00:32.420 I'm going to create a class called ImperativeVsDeclarativeExample2. I am going to make this class executable 5 00:32.420 --> 00:35.090 by adding a public static void main method. 6 00:39.060 --> 00:42.560 First step is we are going to create the input list. 7 00:42.900 --> 00:44.580 Going to be the list of Integers. 8 00:47.840 --> 00:55.640 and then lets give it a name in integerList. Lets import this list. It's going to be I'm going to use the Arrays 9 00:55.640 --> 01:10.030 class dot as Arrays.asList() method and then I'm going to pass the put values 1 2 2 3 3 4 5 5 6 7 8 8 9 and 10. 10 01:10.070 --> 01:19.050 So the use case is we want to remove all the duplicates from it and then have the list with the unique values. 11 01:19.730 --> 01:25.460 If we have to code this in a imperative approach, how do we do it? The way we do it is. Let me give some code 12 01:25.460 --> 01:29.160 comments here. First step is we are going to do the imperative approach. 13 01:31.420 --> 01:36.160 Followed by that we are going code the Declarative approach. 14 01:38.810 --> 01:44.430 In the imperative approach, First step is I am going to create a list. 15 01:44.500 --> 01:53.260 This is going to hold the output. I'm going to name it as a unique list and then lets initialize this. 16 01:54.130 --> 01:54.580 There you go. 17 01:54.630 --> 01:56.760 Now we have the unique list available. 18 01:56.870 --> 02:05.950 The next step is I am going to iterate this list Integer integer : integerList. 19 02:06.270 --> 02:19.520 And what I'm going to do, I'm going to check if uniqueList.contains(integer) . If the list contains the integer 20 02:19.520 --> 02:22.650 then that means that value is already there 21 02:22.670 --> 02:24.680 Then I want to skip that value. Right ? 22 02:24.770 --> 02:27.850 So this not condition is going to help me achieve that. 23 02:28.160 --> 02:36.540 And then I'm going to add only if that integer is not part of the unique list and then I will add this. 24 02:36.540 --> 02:43.480 This is the Imperative style. Basically we iterate the list and we check for it basically to find out whether 25 02:43.510 --> 02:45.850 that element is part of that unique list or not. 26 02:45.990 --> 02:52.910 If it is not there that means it is a unique value and we will add that value to this list. 27 02:52.980 --> 02:54.240 I'm going to print this value. 28 02:57.570 --> 03:04.860 There you go ! And run this and check the result.Going to run this program. 29 03:05.850 --> 03:08.240 Gave the unique list here. 30 03:08.520 --> 03:14.070 Let's see how we can achieve the same logic in a declarative way. 31 03:14.320 --> 03:18.750 Basically we are not going to write the logic on how to find the uniqueness. 32 03:18.760 --> 03:24.680 We are going to make use of the functions that are already present as part of the Java8. 33 03:24.730 --> 03:29.920 Basically Java8 is released with a bunch of functions and lots and lots of functions are available. 34 03:29.920 --> 03:36.700 We just have to find the right function and then use it. This course is going to help you understand all the 35 03:36.700 --> 03:40.030 functions that are released as part of Java8. 36 03:40.270 --> 03:46.750 Now the first step is I'm going to use the source the source is going to be the integer list and then 37 03:46.780 --> 03:51.840 if you take a look at it there is a new method called stream() that got introduced as part of Java8. 38 03:52.390 --> 03:55.670 And what we're going to do was we are going to call a method called distinct. 39 03:55.720 --> 04:02.650 This is like in SQL we perform the distinct in order to get the unique set of values from the table. 40 04:02.950 --> 04:04.520 It's going to be a similar concept. 41 04:04.720 --> 04:07.050 And then we want to collect the values right. 42 04:07.060 --> 04:11.600 We want to collect. There is something called collectors. 43 04:11.600 --> 04:13.640 How do you want to collect what collection you want ? 44 04:13.640 --> 04:17.580 I want to collect as a list. 45 04:17.750 --> 04:19.880 Now I'm going to give it a name. 46 04:20.150 --> 04:22.000 List 47 04:25.480 --> 04:33.090 and integer list one or we can name it as uniquelist1. I'm going to print it here. 48 04:37.040 --> 04:41.610 There you go. Now let's run this and verify the result. 49 04:43.890 --> 04:46.740 There you go, t gave you the same result as this one. 50 04:46.820 --> 04:52.250 But if you take a look at the code readability wise here we are just calling some functions we 51 04:52.270 --> 04:58.500 don't worry about how it is implemented. The system or the functions that got released as part of the language. 52 04:58.510 --> 05:03.290 It takes care of performing the operation that you requested and it gives you the result. 53 05:03.460 --> 05:10.030 So this is one of the advantage of the declarative programming. We just call the appropriate functions 54 05:10.270 --> 05:15.550 based on your use case and it is going to perform the work and give you the result that you are looking 55 05:15.550 --> 05:16.120 for. 56 05:16.360 --> 05:22.440 So all you have to do is build your knowledge on the functions that are available and use them as per 57 05:22.450 --> 05:24.150 your use case. 58 05:24.250 --> 05:27.130 But this we came to the end of this tutorial. Thank you for watching.