README

$ ls
Bar.scala  Foo.java
$ javac *.java && scalac *.scala
$ scala Bar
Foo: hi
Bar: hi

Bar.scala

object Bar{

  trait Bar extends Foo {
    override def foo(s: String) = {
      super.foo(s)
      println("Bar: "+s)
    }
  }

  def main(arg: Array[String]) = {
    (new Bar{}).foo("hi")
  }
}

Foo.java

class Foo{
  public void foo(String bar){
    System.out.println("Foo: "+bar);
  }
}