/**
* A sensible definition of {@link #retainAll} in terms of {@link #iterator}, using the iterator's
* {@code remove} method. If you override {@link #iterator}, you may wish to override {@link
* #retainAll} to forward to this implementation.
*
* @since 7.0
*/
protected boolean standardRetainAll(Collection<?> collection) {
return Iterators.retainAll(iterator(), collection);
}
@Override
public boolean retainAll(Collection<?> c) {
synchronized (mutex) {
return Iterators.retainAll(delegate().iterator(), c);
}
}
/**
* Removes, from an iterable, every element that does not belong to the provided collection.
*
* <p>This method calls {@link Collection#retainAll} if {@code iterable} is a collection, and
* {@link Iterators#retainAll} otherwise.
*
* @param removeFrom the iterable to (potentially) remove elements from
* @param elementsToRetain the elements to retain
* @return {@code true} if any element was removed from {@code iterable}
*/
public static boolean retainAll(Iterable<?> removeFrom, Collection<?> elementsToRetain) {
return (removeFrom instanceof Collection)
? ((Collection<?>) removeFrom).retainAll(checkNotNull(elementsToRetain))
: Iterators.retainAll(removeFrom.iterator(), elementsToRetain);
}