gistfile1.txt

scala> import java.util.{Map => JMap, HashMap => JHashMap}
import java.util.{Map=>JMap, HashMap=>JHashMap}

scala> import java.io.Serializable
import java.io.Serializable

scala> type SerializableMap[A,B] = JMap[A,B] with Serializable
defined type alias SerializableMap

scala> def process[A,B]( key:A,value:B,m:SerializableMap[A,B]) = {
     |   m.put(key,value)
     |   m
     | }
process: [A,B](key: A,value: B,m: SerializableMap[A,B])SerializableMap[A,B]

scala> class MySerializableMap[A,B] extends JHashMap[A,B] with Serializable
defined class MySerializableMap

scala> val sm:SerializableMap[String,Int] = new MySerializableMap[String,Int]
sm: SerializableMap[String,Int] = {}

scala> process("foo",1,sm)
res1: SerializableMap[String,Int] = {foo=1}

scala> def process2[A,B]( key:A,value:B,m:JMap[A,B] with Serializable) = {
     |   m.put(key,value)                                                 
     |   m                                                                
     | }
process2: [A,B](key: A,value: B,m: java.util.Map[A,B] with java.io.Serializable)java.util.Map[A,B] with java.io.Serializable

scala> process2("bar",2,sm)
res3: java.util.Map[String,Int] with java.io.Serializable = {foo=1, bar=2}