scala - 关于用 JavaConverters 替换 JavaConversions

Question

当我尝试运行基于 this example 的代码时，我收到以下警告:

warning: object JavaConversions in package collection is deprecated (since 2.12.0): use JavaConverters

AFAICT，负责警告的行是这些:

import scala.collection.JavaConversions._

/* ... */

    for ((k,v) <- environmentVars) println(s"key: $k, value: $v")

更换 import符合

import scala.collection.JavaConverters._

...是不足够的;单独这样做会导致错误:

error: value withFilter is not a member of java.util.Map[String,String]
    for ((k,v) <- environmentVars) println(s"key: $k, value: $v")

还必须做什么？

Answer 1

您需要添加 asScala方法:

import scala.collection.JavaConverters._

for ((k,v) <- environmentVars.asScala) println(s"key: $k, value: $v")

从 Scala 2.13 开始，现在是 CollectionConverters :

import scala.jdk.CollectionConverters._

for ((k,v) <- environmentVars.asScala) println(s"key: $k, value: $v")