How to convert from from java.util.Map to a Scala Map

Question

A Java API returns a java.util.Map;. I would like to put that into a Map[String,Boolean]

So imagine w

Answer 1

A Scala String is a java.lang.String but a Scala Boolean is not a java.lang.Boolean. Hence the following works:

import collection.jcl.Conversions._
import collection.mutable.{Map => MMap}
import java.util.Collections._
import java.util.{Map => JMap}

val jm: JMap[String, java.lang.Boolean] = singletonMap("HELLO", java.lang.Boolean.TRUE)

val sm: MMap[String, java.lang.Boolean] = jm //COMPILES FINE

But your problem is still the issue with the Boolean difference. You'll have to "fold" the Java map into the scala one: try again using the Scala Boolean type:

val sm: MMap[String, Boolean] = collection.mutable.Map.empty + ("WORLD" -> false)
val mm = (sm /: jm) { (s, t2) => s + (t2._1 -> t2._2.booleanValue) }

Then mm is a scala map containing the contents of the original scala map plus what was in the Java map