WEBVTT 00:00.320 --> 00:00.860 Hi everyone. 00:00.860 --> 00:02.000 Welcome back to this tutorial. 00:02.000 --> 00:06.460 In this tutorial we will code and explore the predicate functional interface. 00:06.470 --> 00:10.520 Let's go ahead and check the abstract method and the other default methods. 00:10.520 --> 00:17.480 This predicate functional interface supports press the shift key twice and then I'm going to search 00:17.480 --> 00:18.860 for predicate. 00:19.310 --> 00:23.000 So this is the predicate interface that we are going to focus on. 00:23.480 --> 00:29.450 Click on this and then this predicate interface is part of the Java.util dot function package. 00:29.990 --> 00:31.880 Take a look at the methods it has. 00:32.280 --> 00:35.480 This is Boolean test and it accepts a input. 00:35.480 --> 00:40.790 So this is an abstract method which we are going to implement as part of the lambda expression. 00:40.790 --> 00:47.360 So this test method accepts an input and it is going to perform some kind of operation on that input 00:47.360 --> 00:49.670 and then it is going to return a Boolean. 00:50.060 --> 00:52.130 That's what predicate is going to do. 00:52.130 --> 00:58.700 And if you take a look at it, it supports some other default methods which are like an operation or 00:58.700 --> 00:59.480 operation. 00:59.480 --> 01:05.760 And negate Operation Negate is basically it is going to reverse the result of the expression that we 01:05.760 --> 01:09.630 are going to implement as part of the boolean, as part of the Lambda expression. 01:10.110 --> 01:12.210 And the next is the is equal method. 01:13.820 --> 01:14.510 What we will do. 01:14.510 --> 01:21.500 Let's go some simple use case and then explore all the different methods this predicate functional interface 01:21.500 --> 01:22.340 supports. 01:23.420 --> 01:25.520 I'm going to create a class called. 01:27.220 --> 01:28.750 Predicate example. 01:31.670 --> 01:36.470 And then let's make this class executable by adding public static void main. 01:36.920 --> 01:41.390 In here, I'm going to create the first predicate. 01:42.230 --> 01:49.040 Functional interface implementation predicate and what the use case that I'm going to do is that, okay, 01:49.040 --> 01:54.050 I'm going to pass an integer check whether that integer is an even number. 01:54.050 --> 01:57.020 That's a use case that we are going to code here. 01:58.360 --> 01:59.960 So it is going to accept an integer. 02:00.830 --> 02:03.830 And then what I'm going to do, I'm going to give a name. 02:05.060 --> 02:08.990 So I'm going to assign a variable because it is accepting an input. 02:10.330 --> 02:15.250 Followed by that, I'm going to open and close the curly braces. 02:15.250 --> 02:17.950 This is where I'm going to give the lambda body. 02:19.130 --> 02:20.930 And it is going to return. 02:22.110 --> 02:26.760 So the use cases, we are going to check whether the past number is even or not. 02:27.610 --> 02:30.190 A modulo two. 02:31.180 --> 02:32.200 Equal to equal to zero. 02:34.150 --> 02:41.470 So we have the lambda expression for the predicate interface ready. 02:41.500 --> 02:44.110 Let's pass some inputs and then test. 02:48.380 --> 02:50.720 Dot p dot test. 02:50.720 --> 02:56.330 I'm going to pass the value as four or is an even number. 02:56.330 --> 02:56.840 Right? 02:56.960 --> 02:58.250 Let's go ahead and run this. 03:00.110 --> 03:01.160 It returned to. 03:02.480 --> 03:03.770 So you might be wondering. 03:03.770 --> 03:08.840 I can do the same operation without the predicate functional interface. 03:08.840 --> 03:09.140 Right. 03:09.170 --> 03:10.490 What's the benefit in here? 03:10.520 --> 03:14.300 The benefit is a code reusability, which we will cover in a bit. 03:14.390 --> 03:20.450 You can reuse the same predicate functional interface n number of times throughout your project. 03:20.840 --> 03:23.090 That was not possible prior to this. 03:23.120 --> 03:31.460 Now, if you take a look at this expression, this is really a simple lambda expression which has one 03:31.460 --> 03:32.430 single statement. 03:32.450 --> 03:39.530 So if you remember or if you recall from our prior tutorials, if the Lambda body is a single statement 03:39.530 --> 03:44.720 or an expression, then we don't even need the curly braces and the return statement. 03:44.840 --> 03:46.190 Or can we rewrite this? 03:47.440 --> 03:49.000 I'm going to rewrite this. 03:50.540 --> 03:52.470 Navy E one. 03:53.220 --> 03:55.070 So I'm going to remove the curly braces. 03:56.260 --> 03:59.740 If you remove the curly braces, you don't even have to use the return keyword. 04:01.040 --> 04:07.370 The syntax is applicable only for single line statement or simple expressions. 04:07.400 --> 04:08.990 Let's go ahead and check this. 04:10.550 --> 04:14.750 The expectation is that both are going to print the same result. 04:15.170 --> 04:16.130 Run this. 04:17.160 --> 04:19.090 We're going to use P one, not P. 04:22.900 --> 04:23.370 There you go. 04:23.380 --> 04:25.720 Both printed the same result. 04:25.720 --> 04:31.330 So we have successfully implemented the predicate functional interface using Lambda expression. 04:31.330 --> 04:37.990 Now let's build this use case to use the other default methods which are part of the functional interface 04:37.990 --> 04:41.950 predicate you're going to use and negate and are. 04:43.580 --> 04:47.360 I'm going to move this to the top so that we can reuse throughout this class. 04:48.950 --> 04:49.700 There we go. 04:55.300 --> 04:58.300 And then I'm going to mark this one as static. 05:01.290 --> 05:04.350 Run this to make sure this is working as expected. 05:07.610 --> 05:10.010 Let's create a method called predicate and. 05:12.760 --> 05:14.740 Public static. 05:16.310 --> 05:17.090 Wired. 05:19.430 --> 05:21.620 The name is going to be decayed. 05:24.090 --> 05:29.460 So we are going to explore the and method as part of the predicate functional interface. 05:29.490 --> 05:37.800 What I'm going to do is I'm going to introduce one more predicate interface, and this is going to check 05:37.800 --> 05:42.420 if the number is divisible by five or not. 05:42.810 --> 05:43.350 Okay. 05:43.350 --> 05:47.820 So in here, what we are going to do, we are going to have the code as. 05:49.990 --> 05:57.730 Doubt we are going to have p one dot you're going to use the and method P two. 05:58.890 --> 06:04.290 You can have n number of P one or n number of predicate interfaces as part of this chain. 06:04.320 --> 06:09.810 Again, as I mentioned, as part of the consumer interface class, this is called predicate. 06:11.020 --> 06:12.520 Painting in here. 06:12.520 --> 06:16.930 What we are going to do, we are going to pass the input using the test method. 06:16.930 --> 06:19.990 You should always use the test method in order to pass the input. 06:20.260 --> 06:22.180 I'm going to pass the input as ten. 06:22.390 --> 06:23.020 Right. 06:23.020 --> 06:27.430 So ten is a number which is divisible by two and it is also divisible by five. 06:27.460 --> 06:30.520 Now what we are going to do, we are going to pass this input. 06:31.980 --> 06:32.730 For this method. 06:34.400 --> 06:35.840 Are we going to call this method? 06:35.930 --> 06:39.350 This method is eventually going to call this one. 06:40.420 --> 06:42.680 The predicate and result is. 06:44.200 --> 06:45.280 So what will be the result? 06:45.280 --> 06:52.450 The result should be true because we're passing a value ten which is divisible by five and also divisible 06:52.480 --> 06:53.110 by two. 06:55.680 --> 06:57.000 Node and then run this. 06:58.330 --> 06:58.840 There you go. 06:59.110 --> 06:59.560 Predicate. 06:59.560 --> 07:00.580 And the result is. 07:03.180 --> 07:06.660 Now what I'm going to do, I'm going to pass the value as nine. 07:09.000 --> 07:14.400 So we are going to have one more result in the console with the value as the result as false. 07:16.860 --> 07:17.790 As expected. 07:17.940 --> 07:20.340 Let's go ahead and check the operation. 07:20.340 --> 07:22.650 I'm going to copy this and then put it here. 07:24.620 --> 07:30.130 Is going to be predicate are in the place of this we are going to use are. 07:30.910 --> 07:32.080 I'm going to replace this one. 07:32.080 --> 07:32.630 Two are. 07:33.730 --> 07:37.990 Indicate our results Indicate our results. 07:39.280 --> 07:40.240 Take a look at it. 07:40.630 --> 07:41.710 Indicate are. 07:42.590 --> 07:43.080 Candice. 07:43.250 --> 07:48.710 Now, let's go ahead and run this right and then check what is the result the result is going to be. 07:49.580 --> 07:53.360 True in both the cases now for true and false in both the cases. 07:55.410 --> 08:00.930 But this one is not divisible by two and also not divisible by five. 08:00.960 --> 08:05.170 Now, what I'm going to do, I'm going to change this value to eight right in here. 08:05.190 --> 08:08.670 Eight is divisible by two, but not divisible by five. 08:08.910 --> 08:10.320 Let's run this and check. 08:11.400 --> 08:14.160 The result is going to be true and true for the AR operation. 08:14.520 --> 08:20.550 As you see here, the result is true and true because our operation is equal to if one of the operation 08:20.550 --> 08:25.920 is one of the result of the operation is true, then it is going to evaluate the result to. 08:27.040 --> 08:29.680 Now what we will do, we will explore the negate method. 08:33.440 --> 08:36.710 Going to be dedicate negate. 08:38.300 --> 08:41.600 Negate is a method which will reverse the result. 08:42.150 --> 08:42.950 So I'm gonna. 08:45.670 --> 08:47.650 Take this one and then. 08:48.670 --> 08:48.970 Negate. 08:49.330 --> 08:55.300 So in the earlier scenario, this expression evaluated to. 08:56.670 --> 08:57.600 What's right. 08:57.600 --> 09:03.570 So this one evaluated to true because one of the operation is true, then it is going to evaluate the 09:03.570 --> 09:05.390 final result also to true. 09:05.430 --> 09:11.520 Here we are using the negate what what the negate will do is negate is going to reverse the result, 09:11.520 --> 09:13.710 whatever that it is going to evaluate. 09:13.710 --> 09:18.450 So p one dot RP2 is going to evaluate the result to true. 09:18.630 --> 09:23.040 The negate operation basically is going to reverse the result to false. 09:23.790 --> 09:26.910 So the result is going to be false. 09:27.300 --> 09:28.290 Call this method. 09:29.720 --> 09:34.430 I'm going to rename this with the correct value predicate negate. 09:37.080 --> 09:38.250 So I'm going to run this method. 09:41.370 --> 09:44.990 As you see, the predicate negate result is false. 09:45.000 --> 09:48.300 But we take a look at the actual or operation result. 09:48.300 --> 09:48.990 It is true. 09:49.570 --> 09:53.560 So these are the different methods which are part of the predicate interface. 09:53.650 --> 10:00.070 In our next tutorial, we will explore our student database and then use the predicate interface as 10:00.070 --> 10:05.660 part of that student collection and then explore more use cases. 10:05.680 --> 10:07.690 With this, we came to the end of this tutorial. 10:07.720 --> 10:08.860 Thank you for watching.