/**
* Creates a set containing all of the elements of the specified collection.
*
* @param c the collection of elements to initially contain
* @throws NullPointerException if the specified collection is null
*/
public CopyOnWriteArraySet(Collection<? extends E> c) {
al = new CopyOnWriteArrayList<E>();
al.addAllAbsent(c);
}
/**
* Adds all of the elements in the specified collection to this set if they're not already
* present. If the specified collection is also a set, the <tt>addAll</tt> operation effectively
* modifies this set so that its value is the <i>union</i> of the two sets. The behavior of this
* operation is undefined if the specified collection is modified while the operation is in
* progress.
*
* @param c collection containing elements to be added to this set
* @return <tt>true</tt> if this set changed as a result of the call
* @throws NullPointerException if the specified collection is null
* @see #add(Object)
*/
public boolean addAll(Collection<? extends E> c) {
return al.addAllAbsent(c) > 0;
}