| 17 |
|
* vastly outnumber mutative operations, and you need |
| 18 |
|
* to prevent interference among threads during traversal. |
| 19 |
|
* <li>It is thread-safe. |
| 20 |
< |
* <li>Mutative operations(add, set, remove, etc) are expensive |
| 20 |
> |
* <li>Mutative operations (add, set, remove, etc) are expensive |
| 21 |
|
* since they usually entail copying the entire underlying array. |
| 22 |
< |
* <li>Iterators do not support the mutative remove operation |
| 23 |
< |
* <li>Traversal via iterators is very fast and cannot ever encounter |
| 22 |
> |
* <li>Iterators do not support the mutative remove operation. |
| 23 |
> |
* <li>Traversal via iterators is fast and cannot encounter |
| 24 |
|
* interference from other threads. Iterators rely on |
| 25 |
|
* unchanging snapshots of the array at the time the iterators were |
| 26 |
|
* constructed. |
| 27 |
|
* </ul> |
| 28 |
< |
* <p> |
| 29 |
< |
* <b>Sample Usage.</b> Probably the main application |
| 30 |
< |
* of copy-on-write sets are classes that maintain |
| 31 |
< |
* sets of Handler objects |
| 32 |
< |
* that must be multicasted to upon an update command. This |
| 33 |
< |
* is a classic case where you do not want to be holding a |
| 34 |
< |
* lock while sending a message, and where traversals normally |
| 35 |
< |
* vastly overwhelm additions. |
| 28 |
> |
* |
| 29 |
> |
* <p> <b>Sample Usage.</b> The following code sketch uses a |
| 30 |
> |
* copy-on-write set to maintain a set of Handler objects that |
| 31 |
> |
* perform some action upon state updates. |
| 32 |
> |
* |
| 33 |
|
* <pre> |
| 34 |
|
* class Handler { void handle(); ... } |
| 35 |
|
* |
| 42 |
|
* |
| 43 |
|
* public void update() { |
| 44 |
|
* changeState(); |
| 45 |
< |
* Iterator<Handler> it = handlers.iterator(); |
| 49 |
< |
* while (it.hasNext()) |
| 45 |
> |
* for (Handler handler : handlers) |
| 46 |
|
* it.next().handle(); |
| 47 |
|
* } |
| 48 |
|
* } |
| 58 |
|
* @param <E> the type of elements held in this collection |
| 59 |
|
*/ |
| 60 |
|
public class CopyOnWriteArraySet<E> extends AbstractSet<E> |
| 61 |
< |
implements Cloneable, java.io.Serializable { |
| 61 |
> |
implements java.io.Serializable { |
| 62 |
|
private static final long serialVersionUID = 5457747651344034263L; |
| 63 |
|
|
| 64 |
|
private final CopyOnWriteArrayList<E> al; |
| 95 |
|
public boolean removeAll(Collection<?> c) { return al.removeAll(c); } |
| 96 |
|
public boolean retainAll(Collection<?> c) { return al.retainAll(c); } |
| 97 |
|
|
| 102 |
– |
public Object clone() { return new CopyOnWriteArraySet(al); } |
| 98 |
|
} |
