Casting the array obtained by invoking the toArray() method on a collection yields a ClassCastException.
String strings = listOfStrings.toArray();
will throw the ClassCastException.
The trick is to use the overloaded version of toArray(), which takes an array as parameter. This the javadoc description of the method
"Returns an array containing all of the elements in this list in the correct order; the runtime type of the returned array is that of the specified array."
The solution is therefore to do this:
String sv = (String)v.toArray(new String);