In Scala, instead of passing a Function<String, Integer>, we pass String => Integer and instead of function.call(a) we write function(a).

scala> def reverseParse(s: String, f: String => Int) = f(s.reverse)
reverseParse: (String,(String) => Int)Int

scala> val c = reverseParse("5632", Integer.parseInt(_))
c: Int = 2365
            

Since functions are first-class we can do other clever things with them, like compose them.

scala> def compose[A, B, C](f: B => C, g: A => B): A => C = (a: A) => f(g(a))
compose: [A,B,C]((B) => C,(A) => B)(A) => C