Can't implement or override java method with type parameters.

[nicolasstucki]

The following code will not compile because it can't match the types method types.

class Coll[E] extends java.util.Collection[E] {
  def toArray[T](a: Array[T]): Array[T] = ???
  ...
}


-- Error: Coll.scala -----------------------------------------------------------
2 |   def toArray[T](a: Array[T]): Array[T] = ???
  |       ^
  |overriding method toArray in trait Collection of type [T] => (x$0: Array[T])Array[T];
  | method toArray of type [T] => (a: Array[T])Array[T] has incompatible type
-- Error: Coll.scala -----------------------------------------------------------
1 |class Coll[E] extends java.util.Collection[E] {
  |      ^
  |class Coll needs to be abstract, since def toArray: [T] => (x$0: Array[T])Array[T] is not defined 
  |(Note that Array[T] does not match Array[T]: their type parameters differ)

two errors found

The same happens when trying to override the method:

class Coll[E] extends java.util.AbstractSet[E] {
  override def toArray[T](a: Array[T]): Array[T] = ???
  ...
}


-- Error: Coll.scala -----------------------------------------------------------
2 |  override def toArray[T](a: Array[T]): Array[T] = ???
  |               ^
  |overriding method toArray in class AbstractCollection of type [T] => (x$0: Array[T])Array[T];
  | method toArray of type [T] => (a: Array[T])Array[T] has incompatible type

one error found