Hey, could someone explain to me, why the following prints true?

val a = "x"
val b = "x"
println(a === b)

This differs from the behaviour that I expected, as the following prints false:

val c = "X".toLowerCase()
println(a === c)

example code: https://pl.kotl.in/NTVgQNuWe

The JVM itself pools constant strings so there's only one instance per string.

Okay thanks, does this affect any other type?

'===' means referential equality and yeah what Karel said^

It also works for boxed integers between -128 and 127, but that's not the JVM that's the

java.lang.Integer

class keeping a cache for the factory function.

all primitive Java types I would say

Yes, for primitive types (int, long, etc.) === and == are the same