WEBVTT 0 00:00.400 --> 00:06.350 Hi Everyone, welcome come back to the tutorial. In this tutorial we will code and explore the consumer functional 1 00:06.470 --> 00:12.860 interface. The consumer functional interface and all the new functional interfaces that got introduced 2 00:13.190 --> 00:16.690 as part of Java 8 are available in the java.util.function 3 00:16.730 --> 00:18.820 java.util.function package. 4 00:18.960 --> 00:21.360 Let's go ahead and explore that first. 5 00:21.410 --> 00:27.110 I'm going to press the shift key twice. Its going to give me this search everywhere window. In here I'm going 6 00:27.110 --> 00:30.220 to search for consumer interface. 7 00:30.220 --> 00:30.830 There you go! 8 00:30.830 --> 00:31.440 It has an "I" 9 00:31.460 --> 00:38.500 icon in it. That means it's an interface. This is the interface which we're going to explore as part of this tutorial. 10 00:38.530 --> 00:39.060 tutorial. 11 00:39.230 --> 00:43.690 Let's go ahead and check that. If you take a look at the consumer function interface. 12 00:43.820 --> 00:49.820 It has the @FunctionalInterface annotation which means this is a functional interface. 13 00:50.000 --> 00:54.570 Next step is if you take a look at it has one method called accept(). 14 00:54.710 --> 00:56.490 It just accepts an input. 15 00:56.570 --> 00:59.660 It doesn't return any output out of it. 16 00:59.900 --> 01:00.650 And then it has another method 17 01:00.660 --> 01:02.460 called default. 18 01:02.720 --> 01:07.820 As I mentioned in the previous tutorial. We'll be exploring more about the default in the upcoming 19 01:07.820 --> 01:08.700 tutorials. 20 01:08.830 --> 01:10.710 For now, there is another method which 21 01:10.830 --> 01:13.020 is part of this functional interface but 22 01:13.050 --> 01:18.370 we are going to explore this method also as part of this tutorial. 23 01:18.560 --> 01:23.140 Let's see what are the different other interfaces which are part of this java.util.function 24 01:23.180 --> 01:25.090 java.util.function package 25 01:25.410 --> 01:30.730 I'm going to click on this icon as you see here this icon is going to take you to the source. 26 01:30.780 --> 01:35.360 If you take a look at it this is part of the rt.jar file 27 01:35.630 --> 01:38.410 and if you take a look at it there is a package called Java. 28 01:38.630 --> 01:42.760 There is another package called "util" and there is another package called "function". 29 01:43.070 --> 01:49.640 All these new interfaces, whatever you see here starting from this BiConsumer and that ends with UnaryOperator. 30 01:49.640 --> 01:55.120 All these things are introduced as part of the Java 8. 31 01:55.490 --> 02:01.320 All these are categories as Functional Interfaces. 32 02:01.420 --> 02:09.490 In short the implementation of consumer is that accept an input and perform some operation on that input. 33 02:09.660 --> 02:10.800 Lets go ahead and code this one. 34 02:13.480 --> 02:16.650 So first step is I am going to create a package called 35 02:17.800 --> 02:19.180 functionalinterfaces. 36 02:22.890 --> 02:25.800 And then I am going to name this class as ConsumerExample. 37 02:33.330 --> 02:41.030 Lets make this class executable by adding the public static void main(). So we have the class ready 38 02:41.060 --> 02:41.700 to run. 39 02:41.840 --> 02:46.390 Let's implement the functional interface by using lambda expression. 40 02:46.520 --> 02:52.570 First step is that Consumer and the type that it is going to accept is String 41 02:52.670 --> 02:58.640 assign a variable. The use case is that this is going to accept the string as an input and then it is going 42 02:58.640 --> 03:03.770 to perform an uppercase operation and then print the value in the console. 43 03:03.810 --> 03:06.690 So open braces () the input type 44 03:06.680 --> 03:13.960 we are assigning a reference variable as "s"and the type is string and then we're going to perform 45 03:15.410 --> 03:21.870 the print operation in the console and then we are going to perform that uppercase operation to the input 46 03:21.990 --> 03:25.800 that is being passed to the consumer functional interface. 47 03:25.950 --> 03:31.060 Now we have created the first implementation of consumer using lambda. 48 03:31.230 --> 03:37.430 The next step is that we're going to learn about how to process or how to pass an input to this Functional interface 49 03:37.430 --> 03:45.230 Functional interface and how it is going to perform the print and uppercase operation on the input that we are going to pass. So 50 03:45.240 --> 03:51.880 use the reference variable that we created which is "c1". After you press the "." we have two methods one 51 03:51.900 --> 03:59.400 is accept() and one is andThen() . Using the accept method we are going to pass the input first "accept()" and then 52 04:00.440 --> 04:03.970 pass the String Java8. Lets check the result 53 04:04.130 --> 04:06.160 I am going to run this program. 54 04:06.810 --> 04:12.470 And we will check the result in the console. So it printed the value JAVA8. 55 04:12.560 --> 04:20.030 But if you look at the text it performed uppercase operation whatever we instructed this consumer functional 56 04:20.030 --> 04:22.190 interface to do. 57 04:22.190 --> 04:28.130 Now let's go ahead and implement some real world examples in the next tutorial. With this we came to the 58 04:28.130 --> 04:29.310 end of tutorial. 59 04:29.450 --> 04:30.350 Thank you for watching !