Question

How can I convert a java.util.Set[String] to a scala.collection.Set with a generic type in Scala 2.8.1?

import scala.collection.JavaConversions._

var in : java.util.Set[String] = new java.util.HashSet[String]()

in.add("Oscar")
in.add("Hugo")

val out : scala.collection.immutable.Set[String] = Set(in.toArray : _*)

And this is the error message

<console>:9: error: type mismatch;  
found   : Array[java.lang.Object]
required: Array[_ <: String]   
val out : scala.collection.immutable.Set[String] = Set(javaset.toArray : _*)

What am I doing wrong?

Answer 1

toArray() called on a java Set will return an array of Object. Since you already imported JavaConversions, asScalaSet will implicitly convert your Java set to a mutable Scala set or use toSet to convert it to an immutable set.

See also Convert Scala Set into Java (java.util.Set)