guava/src/com/google/common/collect/Multisets.java
static boolean removeAllImpl(Multiset<?> self, Collection<?> elementsToRemove) {
    Collection<?> collection =
        (elementsToRemove instanceof Multiset)
            ? ((Multiset<?>) elementsToRemove).elementSet()
            : elementsToRemove;

    return self.elementSet().removeAll(collection);
  }
static boolean removeAllImpl(Multiset<?> self, Collection<?> elementsToRemove) {
    Collection<?> collection =
        (elementsToRemove instanceof Multiset)
            ? ((Multiset<?>) elementsToRemove).elementSet()
            : elementsToRemove;

    return self.elementSet().removeAll(collection);
  }
An implementation of {@link Multiset#removeAll}.