Method retainAll

corpus/java/training/guava/collect/Iterables.java:155–160

Removes, from an iterable, every element that does not belong to the provided collection. This method calls Collection#retainAll if iterable is a collection, and Iterators#retainAll otherwise. @param removeFrom the iterable to (potentially) remove elements from @param el

(Iterable<?> removeFrom, Collection<?> elementsToRetain)

   * @return {@code true} if any element was removed from {@code iterable}
   */
  @CanIgnoreReturnValue
  public static boolean retainAll(Iterable<?> removeFrom, Collection<?> elementsToRetain) {
    return (removeFrom instanceof Collection)
        ? ((Collection<?>) removeFrom).retainAll(checkNotNull(elementsToRetain))
        : Iterators.retainAll(removeFrom.iterator(), elementsToRetain);
  }

  /**
   * Removes, from an iterable, every element that satisfies the provided