In the above example, we have created one interface named as “ExampleInterface” and inside that we have a couple of abstract properties and methods all together. The keyword “interface” is used to define an interface in Kotlin as shown in the following piece of code.įun sayHello() = 'Hello there' // method with default implementation In this chapter, we will learn more about it. We have already introduced an example with an interface in Chapter 6 - section “anonymous inner class”. An interface can be implemented by a class in order to use its defined functionality. In Kotlin, the interface works exactly similar to Java 8, which means they can contain method implementation as well as abstract methods declaration. In this chapter, we will learn about the interface in Kotlin. If I assign an Int value like this subject = 12 or a double value like this subject = 123.45 Android Studio will show an error message and code will not compile.Īs Kotlin has recognized subject’s data type as String we can only assign String values to it later.

In above case as we have initially added a String value to the variable named subject, therefore Kotlin will recognize subject’s data type as String. Kotlin intelligently define the data type by considering the value of the variable. We will discuss more on explicitly declaring data type later in this course. Unlike Java, In Kotlin explicitly declaring data type is optional.

Kotlin smart enough to recognize the end of the statement. In Kotlin we start with var keyword, then the identifier of the variable, equals sign and the value of the variable. In java we write the data type first, then the identifier of the variable, equals sign, value of the variable and end it with a semicolon.

If we had used Java above code would have looked like this.

Kotlin with keyword