CODEWITHSUNDEEP
scalaset
Twistleton
Twistleton

Reputation: 2935

Convert java.util.Set to scala.collection.Set

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?

Upvotes: 27

Views: 22459

Answers (3)

Viswanath
Viswanath

Reputation: 1551

That's an outdated answer. One needs to import

import scala.jdk.CollectionConverters.*

as shown in https://docs.scala-lang.org/overviews/collections-2.13/conversions-between-java-and-scala-collections.html

and then use .asScala or .asJava method based on the target collection type.

Upvotes: 0

oluies
oluies

Reputation: 17831

Use JavaConverters instead 

import scala.collection.JavaConverters._

val out = in.asScala

out: scala.collection.mutable.Set[String] = Set(Hugo, Oscar)

Upvotes: 27

Mark Jayxcela
Mark Jayxcela

Reputation: 985

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)

Upvotes: 16

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