Method Summary for Abstract Collection - Continued
boolean isEmpty() Returns true if this collection contains no elements. abstract Iterator iterator() Returns an iterator over the elements contained in this collection.
boolean remove(Object o) Removes a single instance of the specified element from this collection, if it is present (optional operation). boolean removeAll(Collection c) Removes from this collection all of its elements that are contained in the specified collection (optional operation). boolean retainAll(Collection c) Retains only the elements in this collection that are contained in the specified collection (optional operation). abstract int size() Returns the number of elements in this collection.