Question

I am new to Scala, trying to integrate some existing Java code with Scala-specific functionality in the Play Framework.

val scalaMap = getScalaMap() // returns Map[String,Seq[String]]

What is a nice clean way to convert scalaMap to use Java collections?

val javaMap = ???  //  java.util.Map<String,List<String>> 

It looks like I want to use JavaConversions, but I’m not sure how to chain together the nested collections. Thanks!

Answer 1

Try this:

import collection.JavaConverters._
val javaMap = scalaMap.mapValues(_.asJava).asJava

It does the job in two steps:

1. first converts Map[String,Seq[String]] to Map[String,java.util.List[String]]

2. then the whole map to Java Map: java.util.Map[String,java.util.List[String]].