WEBVTT 00:00.140 --> 00:00.680 Hi everyone. 00:00.680 --> 00:01.310 Welcome back. 00:01.310 --> 00:06.920 In this lecture we will code and learn about the different options that are available for subclasses 00:06.920 --> 00:08.780 that extend a sealed class. 00:08.780 --> 00:14.930 So far we have seen the car class extending the vehicle class and the truck class extending the vehicle 00:14.930 --> 00:22.940 class and the final modifier in the car class ensures that no other class can extend the car class right, 00:22.940 --> 00:24.920 so there are no surprises over there. 00:24.920 --> 00:26.480 This is plain and simple. 00:26.480 --> 00:31.730 The next option is we can also add a sealed modifier to the car class. 00:31.730 --> 00:36.950 So this ensures that inheritance is allowed from the car class. 00:36.950 --> 00:43.220 This means other classes can still extend the car class, but controlled for classes that is defined 00:43.220 --> 00:45.230 after the permits keyword. 00:45.230 --> 00:47.330 So in this case we have a flying car. 00:47.360 --> 00:51.290 This means the flying car class can extend the car class. 00:51.290 --> 00:54.140 No other class is allowed to extend the car class. 00:54.140 --> 00:58.190 So what this means is that the subclasses can also be sealed. 00:58.190 --> 01:03.230 The next option is that you can also define the subclass to be Non-sealed. 01:03.230 --> 01:07.010 So in this case any class can extend the subclass car. 01:07.010 --> 01:12.560 So this disable the controlled inheritance behavior that comes with the sealed class. 01:12.560 --> 01:18.680 So this is to break the control inheritance and then opening up the car class to be extended by any 01:18.680 --> 01:19.520 other class. 01:19.520 --> 01:22.100 So basically these are the options that are available. 01:22.100 --> 01:23.840 Let's look at these in action. 01:23.840 --> 01:25.460 So I'm back in IntelliJ here. 01:25.460 --> 01:28.160 So in here we are in the vehicle class right now. 01:28.160 --> 01:32.720 So the very first thing that I'm going to do is I'm going to go to the car class and then mark this 01:32.720 --> 01:34.040 class as okay. 01:34.040 --> 01:37.700 So in this case as soon as I type in the sealed keyword. 01:37.700 --> 01:43.310 So what you have to do is you need to make sure you have permits present in this car class. 01:43.340 --> 01:49.340 So in this case if you go and mouse over here it tells us like sealed classes must have subclasses. 01:49.340 --> 01:51.950 So in this case we can have permits. 01:51.950 --> 01:54.320 I'm going to create a class named flying car. 01:54.440 --> 01:54.800 Okay. 01:54.830 --> 01:57.290 So flying car is one of the type of the car. 01:57.290 --> 02:00.440 So currently electric cars are the talk of the town. 02:00.440 --> 02:06.110 So maybe many generations from now you might see flying cars become really popular. 02:06.140 --> 02:08.210 So in this case let's go ahead and create this class. 02:08.210 --> 02:10.460 So we'll create the class named Flying Car. 02:10.460 --> 02:12.980 And it's going to be part of the seal package. 02:12.980 --> 02:18.230 And in this case this needs to be defined with non sealed final or sealed. 02:18.230 --> 02:21.620 So I'm going to mark this class with a final class modifier. 02:21.620 --> 02:23.990 So this resolves a compilation issue. 02:24.020 --> 02:25.670 Now if you go to the car class. 02:25.670 --> 02:30.800 So the car class is now a sealed class with one another class in the hierarchy. 02:30.800 --> 02:32.870 So this is one of the options that we saw. 02:32.900 --> 02:36.080 And this is how you actually implement the behavior. 02:36.080 --> 02:39.410 So now what I'm going to do I'm going to go to the vehicle class. 02:39.410 --> 02:43.400 And let's see how we can implement the non sealed modifier in the truck class. 02:43.400 --> 02:45.950 So in the truck class currently we have it as final. 02:45.950 --> 02:49.340 So what I'm going to do I'm going to comment this out and put it over here. 02:49.340 --> 02:51.800 And we can add the non sealed modifier. 02:51.800 --> 02:57.360 So what this actually means is that any other class can extend the class. 02:57.360 --> 02:59.970 So in this case, if you go to the dog class over here. 03:00.000 --> 03:03.480 Now dog class may be able to extend the truck class. 03:03.480 --> 03:04.350 Let's try that. 03:04.380 --> 03:05.820 So extend truck. 03:05.820 --> 03:11.760 So this is allowed as soon as you mark the subclass as Non-sealed this behavior will be allowed. 03:11.760 --> 03:14.190 But actually this is not the right practice. 03:14.190 --> 03:15.270 So I'm going to remove it. 03:15.270 --> 03:20.970 But what I want to show you is that when you mark the subclass as Non-sealed, you are going to open 03:20.970 --> 03:22.380 it up for any other class. 03:22.380 --> 03:28.110 To extend this class, it's totally up to the business functionality, how you want to implement your 03:28.110 --> 03:31.320 subclasses, and how restrictive you want the subclasses to be. 03:31.320 --> 03:37.320 So these are the options that we have when it comes to dealing with the subclasses of the sealed classes. 03:37.320 --> 03:40.800 So we saw the Non-sealed class and we saw the final one already. 03:40.800 --> 03:44.100 And then we saw the sealed class of the subclass two. 03:44.100 --> 03:45.960 So this is a very simple example. 03:45.960 --> 03:51.390 In the future part of the course, we are going to implement a real time example using all the concepts 03:51.390 --> 03:52.950 that we have learned so far. 03:52.980 --> 03:54.210 This marks the end of this lecture. 03:54.210 --> 03:55.410 Thank you for watching.