Mastering High Performance with Kotlin

Capturing and non-capturing lambdas

A closure is also known as a capturing lambda because it captures a variable from outside. Java doesn't allow captured local variables to be modified inside an inner-anonymous class or a lambda. This is because the lambda or instance of the inner-anonymous class can be passed to another thread, and if two threads can modify the same variable this can lead to a race condition. This restriction prevents multithreading issues. Kotlin allows you to modify a local variable inside a lambda:

fun main(args: Array<String>) {    var counter = 0    val inc = {

        counter ++    }    inc()}

The decompiled Java code looks like this:

public static final void main(@NotNull String[] args) {   Intrinsics.checkParameterIsNotNull(args,