How can I pass a Scala object reference around in Java?

Question

I want to return from a Java method a reference to a Scala object. How can I do that?

My Scala objects are like this:

trait Environment 

object Loca         


        

Answer 1

While the $.MODULE$ method works, a slightly less jarring way to get Java-interop with Scala objects is to expose the object as a method on itself.

The Scala:

object LocalEnvironment extends Environment{
   def instance = this
}

The Java:

Environment getEnvironment() { return LocalEnvironment.instance(); }  

This works because under the covers, .instance() is implemented as a static method on class LocalEnvironment. There has been some discussion about Scala objects getting an "instance" method by default, for just this purpose.