Ran into some very strange behavior. Why does it matter when I call

::class

?

val c1 = Int::class.java to 42::class.java 
c1.first to c1.second // (int, int)

val c2 = Int::class.java to 42
c2.first to c2.second::class.java // (int, class java.lang.Integer)

Kotlin doesn't make a difference between primitive JVM types and their boxed variant in the language itself, but they still exist under the cover. If you're calling

::class

on a value that was previously boxed (when being stored in a generic

Pair

object), it's not the same as calling it on an unboxed literal

thanks! that makes sense i found i can use an apache util:

ClassUtils.primitiveToWrapper(x)

looking at their implementation, they just keep a hardcoded map of primitives to boxed types.. nothing clever about it

there is also

Int::class.javaObjectType
Int::class.javaPrimitiveType