edu.oswego.cs.dl.util.concurrent
Class CopyOnWriteArraySet
java.lang.Object
|
+--java.util.AbstractCollection
|
+--java.util.AbstractSet
|
+--edu.oswego.cs.dl.util.concurrent.CopyOnWriteArraySet
- All Implemented Interfaces:
- Cloneable, Collection, Serializable, Set
- public class CopyOnWriteArraySet
- extends AbstractSet
- implements Cloneable, Serializable
This class implements a java.util.Set that uses a
CopyOnWriteArrayList for all of its operations.
Thus, it shares the same basic properties:
- It is best suited for applications in which set sizes generally
stay small, read-only operations
vastly outnumber mutative operations, and you need
to prevent interference among threads during traversal.
- Mutative operations(add, set, remove, etc) are fairly expensive
since they usually entail copying the entire underlying array.
- Loops involving repeated element-by-element mutative operations
are so expensive that they should generally be avoided.
- Iterators do not support the mutative remove operation
- Traversal via iterators is very fast and cannot ever encounter
interference from other threads. Iterators rely on
unchanging snapshots of the array at the time the iterators were
constructed
Sample Usage. Probably the main application
of copy-on-write sets are classes that maintain
sets of Handler objects
that must be multicasted to upon an update command. This
is a classic case where you do not want to be holding a synch
lock while sending a message, and where traversals normally
vastly overwhelm additions.
class Handler { void handle(); ... }
class X {
private final CopyOnWriteArraySet handlers = new CopyOnWriteArraySet();
public void addHandler(Handler h) { handlers.add(h); }
private long internalState;
private synchronized void changeState() { internalState = ...; }
public void update() {
changeState();
Iterator it = handlers.iterator();
while (it.hasNext())
((Handler)(it.next()).handle();
}
}
[ Introduction to this package. ]
- See Also:
CopyOnWriteArrayList
, Serialized Form
CopyOnWriteArraySet
public CopyOnWriteArraySet()
- Constructs an empty set
CopyOnWriteArraySet
public CopyOnWriteArraySet(Collection c)
- Constructs a set containing all of the elements of the specified
Collection.
size
public int size()
- Overrides:
size
in class AbstractCollection
isEmpty
public boolean isEmpty()
- Overrides:
isEmpty
in class AbstractCollection
contains
public boolean contains(Object o)
- Overrides:
contains
in class AbstractCollection
toArray
public Object[] toArray()
- Overrides:
toArray
in class AbstractCollection
toArray
public Object[] toArray(Object[] a)
- Overrides:
toArray
in class AbstractCollection
clear
public void clear()
- Overrides:
clear
in class AbstractCollection
iterator
public Iterator iterator()
- Overrides:
iterator
in class AbstractCollection
remove
public boolean remove(Object o)
- Overrides:
remove
in class AbstractCollection
containsAll
public boolean containsAll(Collection c)
- Overrides:
containsAll
in class AbstractCollection
addAll
public boolean addAll(Collection c)
- Overrides:
addAll
in class AbstractCollection
removeAll
public boolean removeAll(Collection c)
- Overrides:
removeAll
in class AbstractSet
retainAll
public boolean retainAll(Collection c)
- Overrides:
retainAll
in class AbstractCollection
add
public boolean add(Object o)
- Overrides:
add
in class AbstractCollection
Submit a bug or feature. Check the Colt home page for the latest news.