WEBVTT 00:00.230 --> 00:00.740 Hi everyone. 00:00.740 --> 00:02.060 Welcome back to this tutorial. 00:02.060 --> 00:05.750 In this tutorial we will talk about constructor reference. 00:06.740 --> 00:10.070 This concept is introduced as part of Java eight. 00:10.100 --> 00:15.860 From the name, it is clear that this concept is related to constructors in Java. 00:16.010 --> 00:20.360 Constructors in Java gets invoked during the creation of an object. 00:21.260 --> 00:22.730 Let's take a look at the syntax. 00:22.820 --> 00:29.780 The syntax is almost the same as the method reference, but here we have the new keyword after the double 00:29.780 --> 00:33.680 colon instead of a method name in method reference. 00:34.550 --> 00:36.890 Let's take a look at some code examples. 00:37.960 --> 00:42.460 You can only use the constructor reference in the context of functional interfaces. 00:42.490 --> 00:47.830 This example here we have the supplier function interface followed by a name, and then in the right 00:47.830 --> 00:50.350 hand side we have the student class. 00:50.500 --> 00:55.400 Followed by that we have this double colon operator and then the new keyword. 00:55.420 --> 01:02.770 What this does is it creates a supplier which is going to return a brand new object whenever the get 01:02.800 --> 01:06.040 method is invoked in this supplier function interface. 01:08.130 --> 01:13.980 The expectation here is that the student class should have an empty constructor if we try to use a similar 01:13.980 --> 01:19.990 syntax to create objects like here, then you will end up having compilation issues. 01:20.010 --> 01:21.630 Let's go ahead and code this one. 01:22.500 --> 01:23.970 When I have the enclosure open. 01:24.000 --> 01:24.480 There you go. 01:24.480 --> 01:25.380 I have the IntelliJ. 01:25.680 --> 01:30.750 And then the next step is I'm going to create a package called constructor reference. 01:33.050 --> 01:34.130 The two reference. 01:36.040 --> 01:40.090 And then what I'm going to do is I'm going to create a class called. 01:41.120 --> 01:42.110 Constructor. 01:43.620 --> 01:47.820 Reference example, I want to make this class executable. 01:49.380 --> 01:49.990 There you go. 01:50.010 --> 01:50.700 It's ready. 01:50.820 --> 01:53.760 The next step is let's create a supplier. 01:53.970 --> 02:01.470 What are we saw in the example and then pass the student as a type to the supplier. 02:02.340 --> 02:03.900 Let's import the player. 02:04.500 --> 02:05.180 There we go. 02:05.190 --> 02:05.910 It's ready. 02:05.910 --> 02:07.730 And then we call student. 02:07.740 --> 02:10.530 We call the name as student supplier for that one. 02:10.800 --> 02:16.290 And then the next thing is we're going to do Student Colon. 02:16.290 --> 02:17.370 Colon New. 02:18.660 --> 02:22.230 Basically this is going to create a student object. 02:22.260 --> 02:24.210 Let's see what it is complaining about. 02:24.780 --> 02:30.090 So as I mentioned in the presentation, we need to have an empty constructor right now. 02:30.090 --> 02:31.620 The student class doesn't have it. 02:31.620 --> 02:33.840 That's the reason why it is complaining about it. 02:34.570 --> 02:37.270 So we have created the student constructor. 02:37.270 --> 02:39.110 Right now we have it. 02:39.130 --> 02:43.300 Now if we go and take a look at it, there is no compilation issue. 02:43.450 --> 02:44.080 It's good. 02:44.410 --> 02:47.020 Let's call this supplier. 02:48.470 --> 02:49.490 He runs a player. 02:51.840 --> 02:52.890 Needs to be. 02:54.430 --> 02:59.350 Prepended with static keyword because we are trying to use that in the static method. 02:59.710 --> 03:02.020 The student supplier dot get. 03:02.860 --> 03:05.800 If you run this, it is going to print an empty object. 03:06.790 --> 03:11.590 Meaning object, which has all the attributes populated as null. 03:11.620 --> 03:12.550 Now. 03:13.350 --> 03:15.300 Let's create one more example of this one. 03:15.300 --> 03:17.670 I'm going to create a function. 03:20.090 --> 03:22.220 Is going to accept a string. 03:23.550 --> 03:27.150 And then the output is going to be student. 03:27.150 --> 03:32.400 So the first parameter here is the input and the second one is the output. 03:32.790 --> 03:35.400 What I'm going to do, I'm going to. 03:37.120 --> 03:37.870 All the same thing. 03:37.950 --> 03:39.430 Shouldn't colon colon new? 03:40.620 --> 03:47.520 Now it will complain because it is expecting one argument or one parameter constructor. 03:47.520 --> 03:51.210 But if you take a look at the student class, we just have these two constructors. 03:51.210 --> 03:55.950 One is an empty constructor and the other one is a constructor which has all the properties. 03:55.980 --> 04:00.990 Now we will have to create the constructor, which takes one argument. 04:01.900 --> 04:03.730 Which is of type string. 04:03.730 --> 04:08.310 And then we are going to set this one as name, this dot name equal to this. 04:09.990 --> 04:13.560 Now if I call this function right? 04:14.510 --> 04:16.100 All this didn't. 04:17.120 --> 04:18.770 Function dot apply. 04:18.800 --> 04:25.120 Because apply is the method which we use in order to pass an input to the function functional interface. 04:25.140 --> 04:27.890 Then I'm going to pass the name as ABC. 04:28.130 --> 04:35.420 If I run, this is going to print the same object, meaning similar object, but name will have ABC 04:35.420 --> 04:36.440 instead of null. 04:38.980 --> 04:39.520 There you go. 04:39.520 --> 04:44.410 It printed the student object, but with the name as ABC. 04:45.680 --> 04:48.020 This is all about constructor reference. 04:48.470 --> 04:50.450 With this we came to the end of this tutorial.