[groovy2shoes]

You don't have to assume that they actually mean anonymous functions. There's no real reason why the Xtend compiler couldn't translate closures to Java objects.

[itsnotvalid]

But by closure I usually refer to the definition of some Lisp books:

  >> a closure is a collection of closed-over variables retained by a function.

I don't really dig deep for what the constructs would produce in memory, but they should be some lambda expression.