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‫Welcome back.

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‫In the last video, you saw the basics of abstract.

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‫And I want to show you a little more about that.

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‫So let's go ahead and and create a cube.

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‫And it's going to it's going to be Ice Cube Baby.

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‫And it's going to have a shape as a cube.

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‫All right.

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‫So this pretty much means that I want to create a cube, and it has to be the shape that we're currently

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‫looking at as a cube.

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‫So we're using this as a keyword in order to say I want to have it as a specific class type, whereas

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‫a specific data type, the data type is cube, and that's the data type that we created ourselves.

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‫It's like saying something as INT.

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‫So I want to have this as an integer, but in this case we don't use a basic data type such as INT,

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‫but we use a data type that we created ourselves.

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‫So what I'm going to do now is I'm going to check if Ice Cube is not null, because if it is null,

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‫then it's not a cube.

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‫But if it's not null, then it will be a cube.

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‫So this means if it is null, we can safely say this shape is no cube, all right, because it just

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‫didn't work to add or put this into a cube.

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‫Because well, if it's not in Cuba, then it will probably, in our case, be a sphere, right?

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‫And then what I can also do is I can check if it is of a certain type, not just by using the double

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‫equal sign and using null.

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‫But I can actually check if the shape is of type cube.

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‫And if that's the case, I can also safely say that this.

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‫Is a cube.

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‫Or this shape is a cube.

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‫All right.

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‫So we use the is keyword to check if a variable is of a certain type.

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‫We use the as keyword in order to create a variable as a certain type.

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‫It doesn't always work, though.

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‫All right.

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‫So now if we run this again, we will once see that this is a shape or the shape is is no cube.

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‫And then we will see that this is a cube, because one of them is a cube, the other one is no cube.

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‫So the first one is a sphere and it says the shape is no cube.

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‫And the next one is this is a cube.

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‫And it says the shape is a cube.

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‫All right.

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‫So now we can see that this actually worked, so we can actually check it.

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‫And in this case, it's super stupid, right?

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‫Because we're just checking it in order to write something onto the console.

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‫But in other cases, it might actually be relevant for your program because then you can do something

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‫with it.

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‫If it is a cube, then you can do something particular, whether you can calculate it or you can adjust

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‫it, or you can store it in a database or whatever.

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‫If it's something else, then you would handle it differently.

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‫Okay, so that's what you can do.

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‫It's pretty cool.

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‫It's part of polymorphism that we're using here.

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‫That's pretty cool.

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‫So you can see you have another functionality that you can use.

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‫Now let's say we want to cast from an object to a cube.

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‫This, of course, only works if the object, in fact, contains a cube.

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‫All right, so let's create a cube.

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‫I'm going to call this one cube one.

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‫And it's going to be a new cube, and it's going to have a radius of seven.

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‫All right.

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‫So now what I can do is I can create a new cube, and I'm going to call this one cube two, which will

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‫cast Cube.

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‫One to a cube.

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‫So what does that mean?

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‫It means that I want to create a new cube called Cube two, and I want to cast Cube one into a cube.

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‫This will, of course, only work if Cube one is, in fact, a cube.

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‫And now we know that it is a cube.

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‫But that's because we programmed it this way.

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‫At the end, it's actually an object.

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‫So it's an object which contains a cube.

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‫So object is the class that is pretty much here supports all classes in the net class hierarchy and

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‫provides low level services to derived classes.

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‫This means that every single class is inheriting from this class called object every class.

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‫And that's the case in C.

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‫That's the case also in Java and other programming languages.

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‫It's then probably any.

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‫So for example, in Kotlin, it's a keyword any which is also the same kind of concept.

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‫Right.

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‫So this object class contains something like two string to hash and if you want to know more, you can

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‫actually check it out.

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‫So keep control key pressed and you can see it has equals reference equals gets hash code get typed

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‫to string.

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‫So these are the methods that every single object has, even though you haven't implemented it.

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‫So you can very quickly see that by.

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‫Using this for, let's say, our shape.

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‫So here.

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‫Shape start to string.

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‫You can see it has this method same as shape dot equals get hashcode, get info and so forth.

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‫So most of those properties that we can see here we haven't implemented, we just have them because

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‫every class is inheriting from object.

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‫All right.

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‫So now.

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‫Let's write something onto the console with our Q two that we have here.

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‫So, C.W., and what I'm going to say is, has a volume of and then just going to pass or print the

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‫volume.

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‫So cube to name and cube to dot volume.

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‫All right.

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‫And this, of course, will only work.

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‫If it actually is a cube, and in our case it is.

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‫So it should work fine.

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‫Now let's run it.

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‫And we can see CUPE has a volume of 300 or 343.

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‫So that's the cube that we created here, CUPE with seven.

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‫All right.

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‫So that's it.

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‫Now, you have seen how to use abstract, how you can work with abstract classes, that when you create

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‫an abstract class that you can of course, create abstract methods which you then have to implement

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‫once a class inherits from this class.

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‫So once a class inherits from shape.

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‫All righty.

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‫I hope you enjoyed this video.

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‫This is another one of those videos where I got feedback.

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‫People asked for it, so I decided to create this specific video.

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‫And if you have any other demands or questions, please let me know in the question section or in discord.