ScalaからJavaのlambdaを簡単に使う ref: http://qiita.com/takaki@github/items/09916abad7fa2ddf09d1

file0.scala

import java.util.Optional

object JavaLambda {
  def main(args: Array[String]) {
    val s = Optional.of("Scala")


    val l = s.map((s:String)=>s.concat("!!!")).get() // Error!!

    println(l)

  }
}

file1.scala

import java.util.Optional
import java.util.function.Function

object JavaLambda {
  def main(args: Array[String]) {
    val s = Optional.of("Scala")

    val mapper = new Function[String, String] {
      override def apply(v1: String):String = v1.concat("!!!")
    }

    val l = s.map(mapper).get()

    println(l)

  }
}

file2.scala

import java.util.Optional
import scala.compat.java8.FunctionConverters._

object Java8Lambda {
  def main(args: Array[String]) {
    val s = Optional.of("Scala")

    val l = s.map(((v: String) => v.concat("!!!")).asJava).get()

    println(l)

  }
}