Scala: Using HashMap with a default value

Wow, I happened to visit this thread exactly one year after I posted my last answer here. 🙂

Scala 2.9.1. mutable.Map comes with a withDefaultValue method. REPL session:

scala> import collection.mutable
import collection.mutable

scala> mutable.Map[Int, String]().withDefaultValue("")
res18: scala.collection.mutable.Map[Int,String] = Map()

scala> res18(3)
res19: String = ""