defining a scala function1 for use by java has wrong types

Question

The problem can be summarised as follows:

I have a class that defines several methods to be called from java. one of them has a signature like:

import java.lang.{Double => JDouble}

def compute(x: Double, fun: Function1[Double,Double]) = ???

or

def compute(x: Double, fun: Double => Double) = ???

when i use javap on any of them, it looks like this:

Double compute(double, scala.Function1<java.lang.Object, java.lang.Object>)

if I use the following aliasing

 import java.lang.{Double => JDouble}
 def compute(x: Double, fun: JDouble => JDouble) = 

it looks correct with javap

public Double compute( double, scala.Function1<java.lang.Double, java.lang.Double>);

Why is this?

Answer 1

In Scala Double extends AnyVal. When you javap this function the nearest super class finds and in case AnyVal the nearest Java super class is Object.