what does "::" mean in kotlin?

Issue

I'm new to Kotlin
I used this code for opening another activity:

startActivity(Intent(this,IntroAndLang::class.java))

current activity and target activity are written in Kotlin

I cant understand why there is not single : instead of :: at IntroAndLang::class.java

Solution

As stated in the docs this is a class reference:

Class References: The most basic reflection feature is getting the runtime reference to a Kotlin class. To obtain the reference to a statically known Kotlin class, you can use the class literal syntax:

val c = MyClass::class
//The reference is a value of type KClass.

Note that a Kotlin class reference is not the same as a Java class reference. To obtain a Java class reference, use the .java property on a KClass instance.

It’s also the syntax for method references as in this simple example:

list.forEach(::println)

It refers to println defined in Kotlin Standard library.

Answered By - s1m0nw1