android/guava/src/com/google/common/collect/Iterables.java
@CanIgnoreReturnValue
  public static <T> boolean addAll(Collection<T> addTo, Iterable<? extends T> elementsToAdd) {
    if (elementsToAdd instanceof Collection) {
      Collection<? extends T> c = Collections2.cast(elementsToAdd);
      return addTo.addAll(c);
    }
    return Iterators.addAll(addTo, checkNotNull(elementsToAdd).iterator());
  }
@CanIgnoreReturnValue
  public static <T> boolean addAll(Collection<T> addTo, Iterable<? extends T> elementsToAdd) {
    if (elementsToAdd instanceof Collection) {
      Collection<? extends T> c = Collections2.cast(elementsToAdd);
      return addTo.addAll(c);
    }
    return Iterators.addAll(addTo, checkNotNull(elementsToAdd).iterator());
  }
Adds all elements in {@code iterable} to {@code collection}.

@return {@code true} if {@code collection} was modified as a result of this operation.