Converting a java.util.Set to java.util.List in Scala

Question

While in a project that is a mix of Scala and Java, I need to convert a Java Set into a Java List while in the Scala portion of the code.

What are some efficient ways of doing this? I could potentially use JavaConverters to convert Java Set -> Scala Set -> Scala List -> Java List. Are there other options that would be more efficient?

Thanks

Answer 1

The Java collection classes provide a constructor that takes a Collection , so why not just use that?

def js2jl[A](s: java.util.Set[A]): java.util.List[A] = new java.util.ArrayList(s)

Nothing Scala-specific beyond the syntax, but that's not a bad thing in this case.

Answer 2

Why don't you do it just as you would in pure Java ? For example :

val mySet : java.util.Set[Integer] = new java.util.HashSet()
mySet.add(5)
val myList : java.util.List[Integer] = new java.util.ArrayList(mySet)
println(myList)

Is that what you want to do ?