Kotlin Interface

An interface in Kotlin is a collection of abstract methods. An interface defines what operations a class can perform, but does not provide any implementation of those operations. In this tutorial, we will discuss how to define and use interfaces in Kotlin.

Syntax

The syntax for declaring an interface in Kotlin is as follows:

interface MyInterface {
    // declare methods here
}

To implement an interface in a class, use the implement keyword:

class MyClass : MyInterface {
    // implement the interface methods here
}

Example

Suppose we want to create an interface that defines a method to calculate the area of a shape. We can define an interface Shape as follows:

interface Shape {
    fun calculateArea(): Double
}

We can now create a class Rectangle that implements the Shape interface:

class Rectangle(val width: Double, val height: Double) : Shape {
    override fun calculateArea(): Double {
        return width * height
    }
}

Output

If we create an object of Rectangle and call the calculateArea() method, it will return the area of the rectangle:

val rectangle = Rectangle(5.0, 3.0)
println(rectangle.calculateArea()) // Output: 15.0

Explanation

Interfaces in Kotlin are similar to interfaces in Java. An interface defines a set of methods that must be implemented by any class that implements the interface. In Kotlin, interfaces can also include default implementations for methods (similar to Java 8) and properties.

In the example above, we defined the Shape interface that defines a method for calculating the area of a shape. We then implemented this interface in the Rectangle class, and provided an implementation for the calculateArea() method using the height and width properties of the rectangle.

Use

Interfaces are a powerful tool in object-oriented programming, allowing for code reuse and separation of concerns. They can be used to define a common set of methods or properties that a group of classes must implement in order to work with a particular system or framework.

Kotlin also supports multiple inheritance of interfaces, allowing a class to implement multiple interfaces.

Important Points

• Interfaces in Kotlin can include default implementations for methods and properties
• An interface only defines a set of methods that must be implemented by the implementing class
• Kotlin supports multiple inheritance of interfaces.

Summary

In this tutorial, we discussed how to define and use interfaces in Kotlin. We covered the syntax, example, output, explanation, use, and important points of interfaces in Kotlin. With this knowledge, you can now use interfaces to define the behavior of classes in your Kotlin applications.