Question

I have a Map[String,String] and a third party function that requires a Map[String,Seq[String]]
Is there an easy way to convert this so I can pass the map to the function?

Answer 1

original.mapValues(Seq(_))

Note that mapValues returns a map view, so the function (Seq(_)) will be recomputed every time an element is accessed. To avoid this, just use normal map:

original.map{ case (k,v) => (k, Seq(v)) }

Usage:

scala> val original = Map("a" -> "b", "c" -> "d")
original: scala.collection.immutable.Map[java.lang.String,java.lang.String] = Map(a -> b, c -> d)

scala> original.mapValues(Seq(_))
res1: scala.collection.immutable.Map[java.lang.String,Seq[java.lang.String]] = Map(a -> List(b), c -> List(d))