Scala/Java ConcurrentHashMap

gistfile1.scala

scala> val mymap = new ConcurrentHashMap[String, Int]
mymap: java.util.concurrent.ConcurrentHashMap[String,Int] = {}

scala> mymap.put("one", 1)
res8: Int = 0

scala> mymap.put("zero", 0)
res9: Int = 0

scala> mymap.get("one")
res10: Int = 1

scala> mymap.get("zero")
res11: Int = 0

scala> mymap.get("two")
res12: Int = 0

gistfile2.scala

scala> val mymap = new ConcurrentHashMap[String, Option[Int]]
mymap: java.util.concurrent.ConcurrentHashMap[String,Option[Int]] = {}

scala> mymap.put("one", Some(1))
res17: Option[Int] = null

scala> mymap.get("two")
res18: Option[Int] = null