Scala与Java SAM互操作,没有2.12 M2标志

在语法和惯用方面,通过创建一些隐式Scala函数将Scala函数转换为Java 8 FunctionalInterface对应类型,似乎可以正常工作.

当然,需要注意的是,这种方法没有利用Java 8通过invokedynamic优化lambda创建的能力.

因此,这种方法导致为Scala函数实例创建JVM对象,与Java 8本机lambda相比,这可能会影响内存使用和性能.

对于硬币的另一面,如何让Java 8 Lambdas伪装成Scala函数,我想有人必须编写一些Java代码来与Scala互操作(如果一个人的目标是拥有一个可调用的Scala API)来自Java).

贾斯汀约翰逊,
关于我的项目发条的微博,
JVM上的XPath / XQuery的新实现,
在Twitter上作为@MartianOdyssey

https://twitter.com/MartianOdyssey

/**
  * Scala Functions masquerading as Java 8 Lambdas.
  *
  * (C) Justin Johansson 2015.
  *
  * Microblogging about my Project Clockwork,a
  * new implementation of XPath/XQuery on the JVM,* as @MartianOdyssey on Twitter (https://twitter.com/MartianOdyssey).
  *
  * Permission to use this code is granted under Apache License,* Version 2.0 and providing attribution is afforded to author,* Justin Johansson.
  */

package lab

import scala.language.implicitConversions

import java.util.{ Arrays => JArrays,List => JList }
import java.util.function.{ Consumer => JConsumer,Function => JFunction,Predicate => JPredicate }
import java.util.stream.{ Stream => JStream }

object JLambda extends App {
  println("JLambda: Scala to Java 8 lambda test")

  implicit def func1ToJConsumer[T](func: T => Unit): JConsumer[T] = {
    new JConsumer[T] {
      def accept(arg: T): Unit = func(arg)
    }
  }

  implicit def func1ToJFunction[T,R](func: T => R): JFunction[T,R] = {
    new JFunction[T,R] {
      def apply(arg: T): R = func(arg)
    }
  }

  implicit def func1ToJPredicate[T](func: T => Boolean): JPredicate[T] = {
    new JPredicate[T] {
      def test(arg: T): Boolean = func(arg)
    }
  }

  val myList = JArrays.asList("cake","banana","apple","coffee")
  println(s"myList = $myList")

  val myListFiltered: JStream[String] = myList.stream
    .filter { x: String => x.startsWith("c") }

  val myListFilteredAndMapped: JStream[String] = myListFiltered
    .map { x: String => x.toUpperCase }

  myListFilteredAndMapped.forEach { x: String => println(s"x=$x") }
}


/*
Outputs:
JLambda: Scala to Java 8 lambda test
myList = [cake,banana,apple,coffee]
x=CAKE
x=COFFEE
*/