Programming Kotlin

Kotlin from Java

Just as Java can be used seamlessly in Kotlin, Kotlin can just as easily be used from your Java programs.

Top-level functions

The JVM does not support top-level functions. Therefore, to make them work with Java, the Kotlin compiler creates a Java class with the name of the package. The functions are then defined as Java methods on this class, which must be instantiated before use.

For example, consider the following top-level function:

    package com.packt.chapter4 
    fun cube(n: Int): Int = n * n * n 

If this is given, the Kotlin compiler will generate a class called com.packt.chapter4.Chapter4 with functions as static members. To use this from Java, we would access this function as we would access any other static method:

 import com.packt.chapter4.Chapter4; ...