code: public static <T> void addAll(Collection<T> collection, Iterable<? extends T> items) {
      for (T item : items) {
        collection.add(item);
      }
    }
docs: Add all the items from an iterable to a collection.
  
  @param <T>
  The type of items in the iterable and the collection
  @param collection
  The collection to which the items should be added.
  @param items
  The items to add to the collection.