WEBVTT 00:00.110 --> 00:00.650 Hi everyone. 00:00.650 --> 00:01.220 Welcome back. 00:01.220 --> 00:06.140 In this lecture we are going to code and learn about the next type of pattern matching called guarded 00:06.140 --> 00:06.770 patterns. 00:06.770 --> 00:10.670 So guarded patterns is an advanced level to the record patterns. 00:10.670 --> 00:13.940 So in this case what we are going to do is we are going to use the same example. 00:13.940 --> 00:18.140 And then we are going to implement the guarded patterns using pattern matching. 00:18.140 --> 00:19.850 So in this case there you go. 00:19.850 --> 00:25.820 So I'm going to name this function as retrieve name using guarded pattern. 00:25.820 --> 00:31.700 So guarded pattern is a kind of a pattern where you can apply checks on the binding variable that we 00:31.700 --> 00:32.690 have over here. 00:33.410 --> 00:39.590 Which here means we don't just rely on the pattern matching on the type and the variable on top of it. 00:39.620 --> 00:41.630 We can apply one another check. 00:41.630 --> 00:47.570 So in this case what we can do is in here the value name can still be null right. 00:47.570 --> 00:51.350 So with this implementation we can still return a null value right. 00:51.380 --> 00:54.200 Which is not desirable as per this functionality. 00:54.200 --> 00:56.840 So in this case what we can do is we can do a when block. 00:56.840 --> 01:05.790 And then we can call when name equal to equal to null return empty string Okay. 01:06.090 --> 01:08.850 Else you return the actual name. 01:08.880 --> 01:13.620 So in this case, we don't need this check anymore because the null is handled on the above case label. 01:13.620 --> 01:17.040 And then what we are going to do we are going to return the name over here. 01:17.070 --> 01:17.640 There we go. 01:17.640 --> 01:24.150 So this is a guarded pattern where we are actually applying the case label for type matching. 01:24.150 --> 01:28.890 On top of it you apply one another check to fulfill your business functionality. 01:28.890 --> 01:31.800 So this specific implementation is a guarded pattern. 01:31.800 --> 01:33.960 This is supported from Java 21. 01:33.960 --> 01:37.110 So in this case what we will do we'll go ahead and write a test over here. 01:37.410 --> 01:39.120 So you go over here. 01:39.120 --> 01:42.780 So rest of the input is going to be behaving as expected. 01:42.780 --> 01:47.700 So in this case if I pass a name as null instead of kitty what would be the response. 01:47.730 --> 01:47.940 Right. 01:47.970 --> 01:52.140 So in this case let's go ahead and write a test case for the new function that we created. 01:52.140 --> 01:52.890 There you go. 01:52.890 --> 01:59.280 And then what I'm going to do I'm going to pass the animal value as instead of this I'm going to be 01:59.280 --> 02:01.290 passing the null over here. 02:01.320 --> 02:03.390 So if I pass a null value over here. 02:03.390 --> 02:05.700 So this is going to give me a empty string. 02:05.700 --> 02:06.060 Right. 02:06.060 --> 02:07.170 So in this case. 02:07.170 --> 02:10.240 So I'm not going to use the method source for this particular test. 02:10.240 --> 02:13.480 I'm going to be passing the empty string over here. 02:13.540 --> 02:13.870 Okay. 02:13.900 --> 02:16.540 So this can be a regular test function. 02:18.550 --> 02:18.850 There you go. 02:18.850 --> 02:20.230 I don't think we need this one. 02:20.290 --> 02:20.770 There we go. 02:20.770 --> 02:23.830 So now what we are going to do we are going to run this test. 02:23.830 --> 02:29.950 So the change we made is we added a null check for the actual record binding variable. 02:29.950 --> 02:33.520 So if this value is null then we are going to be returning the empty string. 02:33.520 --> 02:34.720 So in this case we are passing. 02:34.750 --> 02:38.560 So in this case we are passing the name of the cat to be null. 02:38.560 --> 02:41.530 So we expect the empty string to be the response. 02:41.530 --> 02:46.210 So the name is going to be this one. 02:46.210 --> 02:50.890 And the expected result is going to be empty string I don't think these are needed. 02:50.890 --> 02:52.330 We can go ahead and remove that. 02:52.360 --> 02:52.840 There you go. 02:52.840 --> 02:53.740 So now what we will do. 02:53.770 --> 02:56.440 We'll go ahead and execute this test case. 02:58.270 --> 02:58.630 There you go. 02:58.660 --> 03:00.430 Our test case passed as expected. 03:00.430 --> 03:05.440 So this is how you implement a guarded pattern on record classes. 03:05.470 --> 03:10.660 I hope you all have a pretty good idea about how to implement guarded patterns on record classes. 03:10.660 --> 03:11.980 This marks the end of this lecture. 03:11.980 --> 03:13.060 Thank you for watching.