edu.emory.mathcs.backport.java.util.concurrent
public class CopyOnWriteArraySet extends AbstractSet implements Serializable
Sample Usage. The following code sketch uses a copy-on-write set to maintain a set of Handler objects that perform some action upon state updates.
class Handler { void handle(); ... } class X { private final CopyOnWriteArraySet<Handler> handlers = new CopyOnWriteArraySet<Handler>(); public void addHandler(Handler h) { handlers.add(h); } private long internalState; private synchronized void changeState() { internalState = ...; } public void update() { changeState(); for (Handler handler : handlers) handler.handle(); } }
This class is a member of the Java Collections Framework.
Since: 1.5
See Also: CopyOnWriteArrayList
Constructor Summary | |
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CopyOnWriteArraySet()
Creates an empty set. | |
CopyOnWriteArraySet(Collection c)
Creates a set containing all of the elements of the specified
collection.
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Method Summary | |
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boolean | add(Object e)
Adds the specified element to this set if it is not already present.
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boolean | addAll(Collection c)
Adds all of the elements in the specified collection to this set if
they're not already present. |
void | clear()
Removes all of the elements from this set.
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boolean | contains(Object o)
Returns true if this set contains the specified element.
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boolean | containsAll(Collection c)
Returns true if this set contains all of the elements of the
specified collection. |
boolean | equals(Object o)
Compares the specified object with this set for equality.
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boolean | isEmpty()
Returns true if this set contains no elements.
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Iterator | iterator()
Returns an iterator over the elements contained in this set
in the order in which these elements were added.
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boolean | remove(Object o)
Removes the specified element from this set if it is present.
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boolean | removeAll(Collection c)
Removes from this set all of its elements that are contained in the
specified collection. |
boolean | retainAll(Collection c)
Retains only the elements in this set that are contained in the
specified collection. |
int | size()
Returns the number of elements in this set.
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Object[] | toArray()
Returns an array containing all of the elements in this set.
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Object[] | toArray(Object[] a)
Returns an array containing all of the elements in this set; the
runtime type of the returned array is that of the specified array.
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Parameters: c the collection of elements to initially contain
Throws: NullPointerException if the specified collection is null
Parameters: e element to be added to this set
Returns: true if this set did not already contain the specified element
Parameters: c collection containing elements to be added to this set
Returns: true if this set changed as a result of the call
Throws: NullPointerException if the specified collection is null
See Also: add
Parameters: o element whose presence in this set is to be tested
Returns: true if this set contains the specified element
Parameters: c collection to be checked for containment in this set
Returns: true if this set contains all of the elements of the specified collection
Throws: NullPointerException if the specified collection is null
See Also: contains
Parameters: o object to be compared for equality with this set
Returns: {@code true} if the specified object is equal to this set
Returns: true if this set contains no elements
The returned iterator provides a snapshot of the state of the set when the iterator was constructed. No synchronization is needed while traversing the iterator. The iterator does NOT support the remove method.
Returns: an iterator over the elements in this set
Parameters: o object to be removed from this set, if present
Returns: true if this set contained the specified element
Parameters: c collection containing elements to be removed from this set
Returns: true if this set changed as a result of the call
Throws: ClassCastException if the class of an element of this set is incompatible with the specified collection (optional) NullPointerException if this set contains a null element and the specified collection does not permit null elements (optional), or if the specified collection is null
See Also: remove
Parameters: c collection containing elements to be retained in this set
Returns: true if this set changed as a result of the call
Throws: ClassCastException if the class of an element of this set is incompatible with the specified collection (optional) NullPointerException if this set contains a null element and the specified collection does not permit null elements (optional), or if the specified collection is null
See Also: remove
Returns: the number of elements in this set
The returned array will be "safe" in that no references to it are maintained by this set. (In other words, this method must allocate a new array even if this set is backed by an array). The caller is thus free to modify the returned array.
This method acts as bridge between array-based and collection-based APIs.
Returns: an array containing all the elements in this set
If this set fits in the specified array with room to spare (i.e., the array has more elements than this set), the element in the array immediately following the end of the set is set to null. (This is useful in determining the length of this set only if the caller knows that this set does not contain any null elements.)
If this set makes any guarantees as to what order its elements are returned by its iterator, this method must return the elements in the same order.
Like the toArray method, this method acts as bridge between array-based and collection-based APIs. Further, this method allows precise control over the runtime type of the output array, and may, under certain circumstances, be used to save allocation costs.
Suppose x is a set known to contain only strings. The following code can be used to dump the set into a newly allocated array of String:
String[] y = x.toArray(new String[0]);Note that toArray(new Object[0]) is identical in function to toArray().
Parameters: a the array into which the elements of this set are to be stored, if it is big enough; otherwise, a new array of the same runtime type is allocated for this purpose.
Returns: an array containing all the elements in this set
Throws: ArrayStoreException if the runtime type of the specified array is not a supertype of the runtime type of every element in this set NullPointerException if the specified array is null