Iterable<E> elements
) Adds all elements to this Set.
Equivalent to adding each element in elements using add,
but some collections may be able to optimize it.
Source
/**
* Adds all [elements] to this Set.
*
* Equivalent to adding each element in [elements] using [add],
* but some collections may be able to optimize it.
*/
void addAll(Iterable<E> elements);