Calling Kotlin from Java

In this tutorial, we will look at how to call Kotlin code from Java. Kotlin is fully interoperable with Java, and it's extremely easy to use Kotlin in a Java project. By the end of this tutorial, you should have a clear understanding of how to use Kotlin functionality within your Java code.

What is Kotlin?

Kotlin is a statically typed programming language developed by JetBrains. It is fully interoperable with Java and is designed to be safer, more concise, and more expressive than Java. It can be used to develop all types of applications that Java can, such as Android apps, server-side applications, and much more.

Interoperability between Kotlin and Java

One of the most significant advantages of Kotlin is its seamless interoperability with Java. You can freely mix Kotlin and Java in your code, and everything will work perfectly. You can call Kotlin code from Java and vice versa, use Kotlin classes in Java, and all the features of the Java standard library are available in Kotlin.

How to Call Kotlin from Java

Let's see how we can call Kotlin functions and use Kotlin classes from Java.

Calling Kotlin Functions from Java

You can call top-level Kotlin functions from Java just like static methods. Let's suppose we have a Kotlin file named MyKotlinFile.kt with a function named myFunction:

fun myFunction(str: String) {
  println("Hello, $str!")
}

You can call this function from a Java file like this:

MyKotlinFileKt.myFunction("World");

The Kt suffix in the class name is added by the Kotlin compiler to avoid name collisions with Java classes.

Using Kotlin Classes and Objects from Java

Creating and using Kotlin objects in Java is as straightforward as using Java objects. Let's say we have a Kotlin class named MyClass:

class MyClass {
  fun sayHello(str: String) {
    println("Hello, $str!")
  }
}

You can create an object of this class in Java and call its methods like this:

MyClass myObject = new MyClass();
myObject.sayHello("World");

Null Safety and Java

Kotlin's null safety is one of its most notable features. In Kotlin, you can specify whether a variable can hold a null value or not. But when you are using Kotlin from Java, keep in mind that Java doesn't have null safety. So, you should check for null values before using Kotlin objects in Java.

Conclusion

Kotlin is a powerful and expressive language that offers seamless interoperability with Java. You can easily call Kotlin functions and use Kotlin classes from Java. The process is straightforward and doesn't require any complex setup. So, why not give it a try and start using Kotlin in your Java projects today?