insertAll method Null safety
override
Inserts all objects of iterable
at position index
in this list.
This increases the length of the list by the length of iterable
and
shifts all later objects towards the end of the list.
The list must be growable.
The index
value must be non-negative and no greater than length.
Implementation
void insertAll(int index, Iterable<E> iterable) {
throw new UnsupportedError("Cannot add to immutable List.");
}