WEBVTT 00:00.240 --> 00:00.920 Hi everyone. 00:00.920 --> 00:01.480 Welcome back. 00:01.480 --> 00:06.280 In this lecture we are going to explore unnamed variables in Java in detail. 00:06.320 --> 00:11.320 I want to explain the concepts first and then we will explore them in action by actually coding it. 00:11.480 --> 00:15.800 In Java 25 there is a new special identifier underscore. 00:15.840 --> 00:23.360 It's a signal to other developers that the variable is intentionally ignored and not needed or used 00:23.360 --> 00:24.000 anywhere. 00:24.320 --> 00:27.120 Here is an example of how this can be used. 00:27.120 --> 00:30.640 In this case, we are parsing an integer from a string. 00:30.640 --> 00:36.360 Let's say if the parsing fails, we just catch the exception and then we ignore the exception. 00:36.360 --> 00:41.320 Basically, we do not do anything with the exception, we just return null over here. 00:41.600 --> 00:45.120 In this kind of scenarios, there is no need to add a variable. 00:45.120 --> 00:50.440 We can actually add this underscore and the code will compile without any issues. 00:50.880 --> 00:52.200 What is the benefit of this one? 00:52.240 --> 00:56.560 Actually, this fundamentally improves the readability of the code. 00:56.560 --> 01:00.070 As a developer, you do not need to pay attention to that variable. 01:00.510 --> 01:06.750 Common places where this can be used are in the catch block, like the example above, or in the case 01:06.750 --> 01:09.510 of lambdas, where only some parameters matter. 01:09.550 --> 01:15.030 We can actually use this underscore in the case of pattern matching where the variable is not used or 01:15.070 --> 01:19.430 needed, then we can actually add the underscore over there to. 01:19.470 --> 01:24.550 Another important point to remember is that if you try to read that variable, then it will throw the 01:24.550 --> 01:25.830 compile time error. 01:26.350 --> 01:28.670 Now let's go ahead and explore this in action. 01:28.710 --> 01:30.190 Let's go back to the IntelliJ. 01:30.430 --> 01:34.390 So in here we are going to be working on the package named Unnamed Variables. 01:34.390 --> 01:38.390 And then you will see a class named Unnamed Variables over here. 01:38.670 --> 01:43.190 So this class is basically a very simple main function that we have over here. 01:43.350 --> 01:47.270 And then we have this get integer function which takes in a string. 01:47.270 --> 01:51.590 And then it's going to do the parsing from the string to an integer. 01:51.710 --> 01:55.790 Here if there is an exception we are actually catching that exception right. 01:55.830 --> 02:01.380 Now what we will do is let's go ahead and write a function that's going to be invoking this particular 02:01.380 --> 02:04.500 function, and then see what the behavior is. 02:04.700 --> 02:07.020 If there is an exception that happened over here. 02:07.060 --> 02:07.460 Okay. 02:07.580 --> 02:12.140 So the exception is something that is being caught with a variable. 02:12.340 --> 02:14.180 But this is not used at all. 02:14.180 --> 02:18.860 So now if we change this to underscore there is no compilation issue over here. 02:18.860 --> 02:20.260 This was not the case before. 02:20.500 --> 02:23.060 Now this is a valid syntax. 02:23.300 --> 02:29.100 In order to make things easy for us, instead of writing the code from scratch, I have created something 02:29.100 --> 02:30.300 called a markdown file. 02:30.540 --> 02:32.780 You'll be able to see markdown file over here. 02:33.460 --> 02:35.980 Let's go ahead and split this to the right. 02:36.380 --> 02:39.620 So this markdown file have two different prompts. 02:39.620 --> 02:45.820 So if you can take a look at it the first prompt is basically the lambda parameters with unnamed variables. 02:45.860 --> 02:50.500 A prompt is something you can think of an input to the large language model. 02:50.500 --> 02:55.220 In this case, it's an AI that we are going to leverage to write the code for us. 02:55.220 --> 02:58.780 So I have one for lambda parameters with unnamed variables. 02:58.780 --> 03:01.740 Other one is exception handling with unnamed variables. 03:01.980 --> 03:04.220 What we are looking at is the exception handling. 03:04.220 --> 03:06.460 So I'm going to be just go to this one. 03:06.700 --> 03:12.580 And then here what this one says is that create a function that demonstrates using the unnamed variables 03:12.580 --> 03:17.340 and exception handling combined with stream operations for parsing the data. 03:17.340 --> 03:22.220 So what I'm doing here is that I'm going to be passing the list of strings, which is going to be an 03:22.220 --> 03:25.260 an invalid integer and a valid integer. 03:25.260 --> 03:27.820 And this is going to call the get integer function. 03:28.140 --> 03:30.980 And this is going to be printing the value which is the. 03:31.020 --> 03:32.620 These are the parsed integer. 03:32.620 --> 03:37.860 So we are going to be converting a list of string into a list of integer. 03:37.860 --> 03:41.020 And those integers are going to be stored in this int list. 03:41.020 --> 03:43.620 So what I'm going to do I'm going to copy this whole prompt. 03:44.260 --> 03:45.980 Go to the assistant. 03:45.980 --> 03:49.100 And you can see that it is pointing to the unnamed variables. 03:49.100 --> 03:53.140 But the one that we want to make the changes to is going to be unnamed variables. 03:53.140 --> 03:59.490 Dot Java okay, so now I'm going to have this over here and then give the prompt and then press send 03:59.490 --> 04:00.170 over here. 04:00.290 --> 04:05.370 So now what this is going to do is that this is going to go ahead and edit the function for us, or 04:05.370 --> 04:07.770 create the function for us in this particular class. 04:07.770 --> 04:11.010 And then you will be able to see the code for yourself. 04:11.130 --> 04:12.450 So now it made the code change. 04:12.450 --> 04:15.290 Let's go ahead and validate the code change. 04:15.450 --> 04:21.410 So in here for the demonstrate exception handling it's going to be talking about multiple unnamed variables. 04:21.410 --> 04:25.210 So it took the list of string right which is 123. 04:25.250 --> 04:28.970 Divide is invalid integer and ten is a valid integer. 04:28.970 --> 04:32.050 So we have a list of string we stream to that one. 04:32.050 --> 04:37.730 And then we call the map function for each and every string that's over here we're calling the get integer. 04:38.010 --> 04:42.130 So in the get integer it's going to be parsing the string to an integer. 04:42.170 --> 04:45.770 If it's a valid one then it is going to return the valid integer. 04:45.770 --> 04:48.050 If it's not this is going to return null. 04:48.330 --> 04:51.450 So now I'm going to accept the change accept all. 04:51.610 --> 04:53.840 And then I'm going to be running this one. 04:54.720 --> 04:55.120 There you go. 04:55.160 --> 04:57.160 We got the result as expected. 04:57.160 --> 04:59.080 So there is an exception, right. 04:59.080 --> 05:01.560 You see that fail to parse divide. 05:01.880 --> 05:04.880 So in this case if you search for this one that code is over here. 05:05.240 --> 05:07.280 So what is a feature we are exploring. 05:07.280 --> 05:09.160 We are exploring the unnamed variables. 05:09.160 --> 05:11.280 In this case this syntax is valid. 05:11.440 --> 05:16.400 And we are also printing what string that failed this particular functionality. 05:16.400 --> 05:18.000 So the string is divide. 05:18.000 --> 05:22.480 So the final list is we have 123 which is a valid integer. 05:22.520 --> 05:23.720 Divide is an invalid. 05:23.720 --> 05:25.280 That's why we have the null over here. 05:25.280 --> 05:28.120 And number ten is basically a valid integer. 05:28.120 --> 05:30.160 So as a result we have this output. 05:30.160 --> 05:37.000 So the beauty here is that we were able to write all these code by just providing this prompt okay. 05:37.040 --> 05:40.520 So this is one of the beauty of using the AI assistant. 05:40.520 --> 05:42.360 You don't have to hand code everything. 05:42.400 --> 05:47.080 As far as you know, what the logic that you are going to be thinking in your head, you just have to 05:47.120 --> 05:52.990 provide that logic as a prompt, and the AI will generate the code for you and write the code for you. 05:52.990 --> 05:55.910 So here I have a very good structured prompt. 05:55.950 --> 05:58.030 You do not have to be like this all the time. 05:58.030 --> 06:04.630 You can actually provide your thoughts in a plain English in a way that you can communicate with the 06:04.670 --> 06:10.270 AA model, similar to how you communicate with ChatGPT, you should be able to communicate with it. 06:10.270 --> 06:16.150 The reason why I have it as a structured prompt with this task, expected function, signature and requirements 06:16.150 --> 06:21.310 is that I want to replicate the code that can actually help with explaining these concepts to you, 06:21.310 --> 06:24.630 but in your case, you don't have to have this exact structure. 06:24.630 --> 06:30.550 You can actually give a prompt as like you interact with your colleague or your fellow developers, 06:30.710 --> 06:33.550 it should be able to generate a reasonable code for you. 06:33.550 --> 06:36.750 But one thing here is that you need to have a clear intent. 06:36.750 --> 06:41.670 So we explored the prompt two, which is using the exception handling with unnamed variables. 06:41.670 --> 06:44.270 And I'm going to be exploring this particular one. 06:44.270 --> 06:49.830 So in this case if you take a look at it we are asking it to create something called demonstrate lambda 06:49.830 --> 06:56.470 with unnamed function, and it's going to take a map of string and integer, but while printing it, 06:56.470 --> 06:59.630 I'm going to be just printing the key and ignoring the value. 06:59.630 --> 07:01.390 So that's why we have this underscore. 07:01.550 --> 07:04.670 This is again to explore the unnamed variables concept. 07:04.670 --> 07:06.350 So let's go ahead and copy this. 07:07.230 --> 07:08.350 Print it over here. 07:08.350 --> 07:12.390 So now I expect the changes to be made in the unnamed variables dot Java file. 07:12.390 --> 07:19.030 So in this course I'm actually going to be using a assistant for some lectures and hand code them for 07:19.030 --> 07:19.630 some lectures. 07:19.630 --> 07:23.110 It's going to be depending on how big of a feature that I'm explaining. 07:23.110 --> 07:23.470 Okay. 07:23.510 --> 07:25.550 So in this case it wrote the function for me. 07:25.550 --> 07:27.430 Let's go ahead and explore this function. 07:27.430 --> 07:31.950 So here you can see that it created the map for me as like I expected it to do. 07:32.230 --> 07:39.350 But in this case for each entry of the map, I'm just going to be taking care of the key and I don't 07:39.350 --> 07:40.510 use the value at all. 07:40.510 --> 07:42.670 So I'm assigning the underscore over here. 07:42.710 --> 07:47.750 Actually, when the code is being written in your source code, you can actually execute this, but 07:47.750 --> 07:51.500 still you'll be able to see the result without even accepting it. 07:51.500 --> 07:53.300 So you have the ability to accept that. 07:53.300 --> 07:55.100 So let's say I'm going to discard it. 07:55.100 --> 07:56.540 Took away all the changes actually. 07:56.540 --> 08:01.460 So now what we can do is that we can copy the same thing, put it here and press enter. 08:01.580 --> 08:04.300 It should be able to write the code for you again. 08:05.260 --> 08:05.740 There you go. 08:05.780 --> 08:07.900 It made the code change for you again. 08:08.180 --> 08:10.460 So this is the beauty of these a assistant. 08:10.500 --> 08:14.340 You have the ability to take away code and ask it to write a new code. 08:14.700 --> 08:18.860 It's all way cheaper to write code using this assistant. 08:18.860 --> 08:20.700 So now I'm going to accept the change. 08:20.940 --> 08:23.460 So we are going to be executing it one more time. 08:23.460 --> 08:23.860 There we go. 08:23.860 --> 08:25.620 So we have just the key over here. 08:25.620 --> 08:29.420 And then we are completely ignoring the value aspect which is underscore. 08:29.460 --> 08:35.540 I hope you all have a pretty good idea about how unnamed variables can be beneficial in expressing the 08:35.540 --> 08:38.140 intent to the developers when they are reading the code. 08:38.180 --> 08:43.380 If there is a underscore that you see in the code, that means that is a variable that is completely 08:43.380 --> 08:43.860 ignored. 08:43.860 --> 08:45.660 You don't have to pay attention to it. 08:45.700 --> 08:47.260 Well, this marks the end of this lecture. 08:47.260 --> 08:48.260 Thank you for watching.