import scala.jdk.CollectionConverters._val s: java.util.Set[String] = Set("one", "two").asJava

scala> import scala.jdk.CollectionConverters._scala> val s = collection.mutable.Set("one")s: scala.collection.mutable.Set[String] = HashSet(one)scala> val js = s.asJavajs: java.util.Set[String] = [one]scala> js.add("two")scala> sres2: scala.collection.mutable.Set[String] = HashSet(two, one)

scala.collection.Iterable       <=> java.lang.Iterablescala.collection.Iterator       <=> java.util.Iteratorscala.collection.mutable.Buffer <=> java.util.Listscala.collection.mutable.Set    <=> java.util.Setscala.collection.mutable.Map    <=> java.util.Mapscala.collection.concurrent.Map <=> java.util.concurrent.ConcurrentMap

scala.collection.Iterable    <=> java.util.Collection   (via asJavaCollection)scala.collection.Iterator    <=> java.util.Enumeration  (via asJavaEnumeration)scala.collection.mutable.Map <=> java.util.Dictionary   (via asJavaDictionary)

scala.collection.Seq         => java.util.Listscala.collection.mutable.Seq => java.util.Listscala.collection.Set         => java.util.Setscala.collection.Map         => java.util.Map

java.util.Properties => scala.collection.mutable.Map

import scala.jdk.CollectionConverters._val source = new scala.collection.mutable.ListBuffer[Int]val target: java.util.List[Int] = source.asJavaval other: scala.collection.mutable.Buffer[Int] = target.asScalaassert(source eq other)