WEBVTT

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Hi everyone.

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Welcome back to this tutorial.

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In this tutorial, I'm going to explain some theory about the default and static methods in interfaces.

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Let's talk about what was allowed before Java eight in interfaces.

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First, the concept of interfaces is to just define the contract, meaning you are just allowed to declare

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the method, but you cannot have any method implementation in interfaces.

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The class that implements the interface should implement the logic for the declared method in the interface.

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We all know that this limitation had a severe impact for an interface to evolve or upgrade because if

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we try to declare new methods in the interfaces, then the class that already implements this interface

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should implement the new method.

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Otherwise this will lead to compilation issues.

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The main impact because of this is for the library creators.

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It was really hard to introduce the new functionality parties in the interfaces.

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In order to avoid this, the Java creators made the change to allow the method implementation in interfaces

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itself via static and default methods.

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Let's talk about the default method first.

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Default methods in interfaces will have the new default keyword as part of the method signature itself,

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which then registers that method as a default method in the interface.

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It is an example of a default method from the list interface.

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This is a short method which is going to sort the list collection.

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If you notice here it has the default keyword as part of the method signature.

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With that, the Java compiler will allow the method implementation in interfaces prior to Java eight.

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We normally use the collections class to perform the similar operation.

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If all methods can be overridden in the implementation class, we will explore all those options in

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our future tutorials.

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If all methods are going to help the Java developers to introduce the new functionalities in the future

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without having any impact to the current classes that implements the interface.

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Similar to default methods.

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We have static methods also allowed as part of the interfaces.

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The only difference between the two meaning between the static method and the default method.

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The static method cannot be overridden in the implementation classes.

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Let's go ahead and explore all these new methods via code in the following tutorials.

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With this we came to the end of this tutorial.

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Thank you for watching.