Working with interfaces in Kotlin

Interfaces in OOP are like the contract. They define the behavior or rules. The classes that implement them need to do so in order to conform to the behavior defined by interfaces. However, that's not it. Interfaces in Kotlin provide much more. Prior to Java 8, we couldn't have the implementation of methods in the interfaces, but in Kotlin, we can have that too! In this recipe, we will see how to deal with interfaces in Kotlin.

Getting ready

I'll be using IntelliJ IDEA for writing and executing code. You are free to use any IDE where you can run the Kotlin code.

How to do it…

As we have just discussed, interfaces in Kotlin can have the implementation of methods; let's follow these mentioned steps to check that out:

1. Let's create an interface named DemoInterface:

interface DemoInterface {

    fun implementatedMethod() {
        println("From demo interface")
    }
}

Defining a method with implementation in the interface is just like you would do inside a class.

2. Now...