Scala generic but unknown parameters

Question

I'm having trouble defining a method using generic parameters in Scala.

Let's say I want a something like this:

class CollectionConverter {
   def convertListToSet(list: java.util.List[SomeType]): java.util.Set[SomeType] = {
     val s = new java.util.HashSet[SomeType]
     s.addAll(list)
     s
   }
}

I can't seem to find a way to make Scala understand that I don't know what SomeType is, just that whatever it is, the returned generic set will have the same generic type as the supplied list. It complains that I haven't defined SomeType. But that's the thing -- I don't know or care what SomeType is, it could be called YeahYeahYeah for all I care.

I don't want to use List[Any], and List[_] creates other problems, so... what's the right way to do this?

Any help would be greatly appreciated!

Kim Stebel · Accepted Answer · 2013-01-06 21:54:55Z

4

That's what type parameters for methods are for.

def convertListToSet[SomeType](list: java.util.List[SomeType]): java.util.Set[SomeType] = {
   val s = new java.util.HashSet[SomeType]
   s.addAll(list)
   s
}

answered Jan 6, 2013 at 21:54

Kim Stebel

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1 Comment

user1953555 Over a year ago

Ahhhhhh so close! So close. Thanks VERY much, that's exactly what I needed.

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