Ran into some very strange behavior. Why does it m...

# getting-started

[poohbar]

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)

[poohbar]

and is there any way for me to make the boxed class object (class java.lang.Integer) from the primitive class object (int)?

[Joffrey]

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

[Joffrey]

If you want to convert between boxed and primitive types, you might want to check out javaPrimitiveType and javaObjectType

[poohbar]

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

[poohbar]

@Joffrey for that, is there a method to give me KClass if I have Class? something like:

String::class.java.kotlin

[poohbar]

oh nvm, this literally works. 🤐

[ephemient]

there is also

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