Kotlin: What can I do when a Java library has an overload of both primitive and boxed type?

Question

For example, FastUtil\'s IntArrayList has a push method that accepts both int (primitive) and Integer (boxed), but Kotlin

Answer 1

Consider these methods in Java:

void f(int x) { }
void f(Integer y) { }

In Kotlin, they are seen as

f(x: Int)
f(x: Int!)

^{The second method has a parameter of platform type, meaning it might be nullable, corresponding to Integer.}

First one can be simply called with Kotlin Int passed:

f(5) // calls f(int x)

To call the second one, you can cast the argument to nullable Int?, thus selecting the overload:

f(5 as Int?) // calls f(Integer y)