WEBVTT

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Hi everyone.

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Welcome back to this tutorial.

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In this tutorial we will code and explore the multiple inheritance in Java.

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For this purpose, I'm going to create three interfaces and one implementation class.

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Let's create the first interface.

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I'm going to create the empty interfaces first and then we will write the default methods.

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I'm going to create the interface.

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I'm going to give it a name as interface one.

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There you go.

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It created the interface for you.

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Now I'm going to create the interface to I'm just copying that interface one class and then putting

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it in the default package.

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And then I'm going to rename that one as interface two.

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Similarly, I'm going to create the interface three to.

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Be right.

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There you go.

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We have all the interfaces created.

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Now, the next step, what I'm going to do, I'm going to create a default method in it.

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The method name is going to be default.

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Method A.

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And this is not going to return anything from it.

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Okay.

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Then this is going to just print.

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Right method.

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Okay.

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Similarly, I am going to create a method B and method C in interface 213.

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So I'm gonna go to the interface.

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To.

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Go there.

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And then let's use the method.

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This is going to be method B, This is going to be method B.

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Go to the interface three.

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The phase three.

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The interface three is going to have the method.

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See?

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There you go.

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Now we have all the interfaces ready.

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Let's go ahead and create the implementation class.

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We're going to create a implementation class called.

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Blind.

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One, two, three.

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Don't ask me why I gave that name.

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I'm just giving that name.

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You want to give some other meaningful name, please go ahead and do it.

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Now, this client, one, two, three is going to.

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Implement the three interfaces that we just created.

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Implement the phase one to phase two.

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And interface three.

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Okay, Now let's go ahead and implement this.

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Now let's go ahead and add the executable method, which is public static, void main.

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We have this ready Now.

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What we will do, we will create an instance of.

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9212, three.

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Equal to new client.

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One, two, three.

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Let's use the client one, two, three instance, and then we will check what are the methods it has

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access to.

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If we take a look at it, it has access to Method A.

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Take a look at the next method.

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As access to Method B.

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It has access to method C?

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Basically, this concept is called multiple inheritance.

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We are inheriting multiple behaviors from each and every interfaces.

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This was never possible before Java eight.

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Now let's go ahead and run this and then see what is getting printed in the console.

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There you go.

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It printed inside method A inside method B, I believe Interface three needs to change this one to interface

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inside method C.

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Run it again.

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There you go.

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Now, what we will do is I'm going to add some complexity into it.

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What I'm going to do, I'm going to have this interface to extends interface.

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One.

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Right.

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So we are building the relationship now.

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I'm going to go back to the implementation class and interface three.

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Extends.

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Interface to.

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There you go.

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So now we have the relationship.

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So interface one doesn't extend anything.

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I'm going to go back and interface two extends interface one and interface three extends interface two.

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So we have a relationship now.

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Now what I'm going to do is I'm going to override the method a implementation in interface two.

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Okay, so I'm going to go to the interface one and copy this.

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I'm an interface to.

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Now, as you notice, I'm going to put this implementation here and then what I'm going to do, I'm

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going to.

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Of the class that it is of the interface that it is getting called.

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With that class, I'm going to do the same thing for Interface one.

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A centrepiece.

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One class.

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Okay when it is going to print, the result is going to print along with the class that is actually

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along with the interface that is actually invoked during the runtime.

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Now, if I call the method, will it print?

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The lager.

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The stout, which is inside the method that is part of interface one or that is part of interface two.

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Basically, we are overriding the method A.

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Now let's go ahead and check which takes the preference.

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Going to run it.

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If you take a look at it, the result it printed the class as interface two.

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What does it mean?

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Is that Java in runtime?

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It is always going to resolve to the child implementation.

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So this is something which you have to keep in your mind.

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Now, let's complicate this.

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What I'm going to do, I'm going to have the default method implementation in the actual implementation

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class itself.

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So if we have it here, as we all know, we cannot have default keyword as part of the class.

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I'm going to change it to public.

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If I have the similar kind of implementation in the.

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Implementation class itself, which takes precedence.

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Now, let's go ahead and run this one.

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If I run this, if we take a look at the result in the console, it printed the value as client one,

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two, three.

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Basically, the class that overrides the default method takes precedence over any other implementation

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that we have in other interfaces.

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Let me summarize on the order of resolving the method call during runtime.

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Number one is.

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Class that implements the interface.

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And number two.

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Us the Subinterface.

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Dot extends the interface, assuming both the methods, both the class and interface have the default

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method overridden from its parent interface.

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So this is something which you have to keep in your mind when you are.

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Overriding the default method in your subinterface or in your implementation class of that interface.

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But this.

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We came to the end of this tutorial.

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Thank you for watching.