Typically, you can't use a 'new' operator on a generic type. This is because of type erasure.
scala> def create[T] = new T
<console>:7: error: class type required but T found
def create[T] = new T
^
Scala gives a way of getting around this problem, with the Manifest class.
scala> def create[T](implicit m:Manifest[T]) = m.erasure.newInstance
create: [T](implicit m: Manifest[T])Any
scala> create[String]
res0: Any = ""
scala> class SomeClass
defined class SomeClass
scala> create[SomeClass]
res1: Any = SomeClass@112356a
The implicit Manifest object passed by the compiler has the details of the generic at runtime. Using a bit more syntactic sugar, create can be rewritten as,
scala> def create[T:Manifest] = manifest[T].erasure.newInstance
create: [T](implicit evidence$1: Manifest[T])Any
This feature is useful in other cases also, like, getting the type of objects in a List at runtime.
scala> def processList[E : Manifest](ls : List[E]) = println(manifest[E].erasure)
processList: [E](ls: List[E])(implicit evidence$1: Manifest[E])Unit
scala> processList(List(1, 3, 5, 7))
int
scala> processList(List("A", "S", "D", "F"))
class java.lang.String