WEBVTT 00:00.230 --> 00:00.770 Hi everyone. 00:00.770 --> 00:02.120 Welcome back to this tutorial. 00:02.120 --> 00:08.120 In this tutorial we'll code another example of when not to use parallel streams. 00:08.120 --> 00:12.950 So we are going to cover a mutable variable that is going to return you. 00:12.950 --> 00:17.420 The result and how parallel stream can affect that behavior. 00:17.420 --> 00:26.390 So the first step, I'm going to create a class called Sum, and this class is going to have a variable 00:26.390 --> 00:29.960 called let me put this in presentation mode. 00:32.880 --> 00:36.120 Private and total. 00:37.770 --> 00:41.400 And then I'm going to create the getter and setter methods for this one. 00:44.510 --> 00:47.060 Click on Generate. 00:48.710 --> 00:52.190 Generate getters and setters and click okay. 00:53.640 --> 00:54.360 What I'm going to do. 00:54.390 --> 01:01.890 I'm going to have a method here called Public void perform sum. 01:02.640 --> 01:12.810 So this method is going to accept an input and then it is going to perform the summation of all the 01:12.810 --> 01:15.750 inputs that it is going to get and then return the result. 01:18.020 --> 01:21.920 So we are going to use this total variable to get the actual result. 01:22.640 --> 01:23.150 Okay. 01:23.150 --> 01:27.260 Now what I'm going to do, I'm going to create a some client class. 01:33.030 --> 01:37.350 So the some client class is going to call this perform some method from it. 01:41.950 --> 01:45.550 Some client make this class executable. 01:46.630 --> 01:49.780 We're adding public static void main. 01:50.980 --> 01:51.880 Public Static. 01:51.880 --> 01:52.870 Void Main. 01:52.900 --> 01:54.340 The class is ready. 01:54.610 --> 01:57.340 I'm going to create an instance of some 02:00.250 --> 02:08.140 and this one is going to be in stream dot range, closed one comma, 1000. 02:09.670 --> 02:13.650 And then first let's check the result. 02:13.660 --> 02:18.220 What is that result that it is going to give you? 02:18.910 --> 02:23.470 So I'm going to run it in sequential stream and then perform the. 02:25.980 --> 02:33.300 Some perform, some basically this is going to pass the values one by one, like one, two, three until 02:33.540 --> 02:36.510 1000, and it is going to perform. 02:36.510 --> 02:38.250 It is going to call the perform some method. 02:38.250 --> 02:40.290 I'm using the method reference syntax here. 02:40.290 --> 02:45.810 So if you go to the perform some, it is accepting an input and it is going to keep updating this variable 02:45.810 --> 02:47.970 and the result is going to be. 02:50.170 --> 02:54.580 Some dot get total get total is going to give you the actual result. 02:54.670 --> 02:56.230 I'm going to run this example. 02:57.490 --> 02:57.980 There you go. 02:58.000 --> 03:00.520 So the result that we're expecting is. 03:03.560 --> 03:04.890 500, 500. 03:04.910 --> 03:07.100 So that is a result which we are expecting. 03:07.100 --> 03:12.260 What I'm going to do, I'm going to run this example in parallel mode, right? 03:12.260 --> 03:20.210 So this is going to split this 1000 into multiple parts and then call this perform some method concurrently. 03:20.210 --> 03:27.140 And we are going to see whether is it returning the result, 505 hundred as an output or not. 03:28.770 --> 03:29.900 I'm gonna run this. 03:31.790 --> 03:36.410 The result that it gave is 448461. 03:36.650 --> 03:39.530 Let's run this again and then check what is the result. 03:40.910 --> 03:44.900 The result that it gave now is 4 to 7 and 396. 03:45.650 --> 03:48.410 I'm going to run it one more time and then check what is the result. 03:50.830 --> 03:55.050 The result that it gave is 424733. 03:55.050 --> 03:59.400 So every time we run this program, it is giving us a different result. 03:59.910 --> 04:06.510 The reason for the different result every time we run is that if you take a look at the code, we are 04:06.510 --> 04:11.220 concurrently accessing this variable and updating this variable. 04:11.250 --> 04:14.520 That's one of the reason why we get different results. 04:14.520 --> 04:16.440 We run the program every time. 04:16.440 --> 04:23.280 So what happens here is that it is splitting that data input into multiple parts and concurrently updating 04:23.280 --> 04:24.200 this variable. 04:24.210 --> 04:31.290 So the recommendation here is that if you have any mutable variable, then do not use parallel streams 04:31.290 --> 04:38.370 at all more than performance, it is going to give you the wrong results in these kind of scenarios. 04:38.370 --> 04:44.430 So this is one thing which we have to keep in our mind when we are going to use parallel streams With 04:44.430 --> 04:46.350 this, we came to the end of this tutorial. 04:46.350 --> 04:47.520 Thank you for watching.