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org.ematgine.utils.concurrent
Class CopyOnWriteArraySet  

java.lang.Object
  java.util.AbstractCollection
      java.util.AbstractSet
          org.ematgine.utils.concurrent.CopyOnWriteArraySet

All Implemented Interfaces:

java.lang.Cloneable, java.util.Collection, java.lang.Iterable, java.io.Serializable, java.util.Set

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public class CopyOnWriteArraySet

extends java.util.AbstractSet

implements java.lang.Cloneable, java.io.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. ]

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Field Summary
protected  CopyOnWriteArrayList	al

 

Constructor Summary

CopyOnWriteArraySet()           Constructs an empty set

CopyOnWriteArraySet(java.util.Collection c)           Constructs a set containing all of the elements of the specified Collection.

 

Method Summary
boolean	add(java.lang.Object o)           Adds the specified element to the set if it is not already present (optional operation).
boolean	addAll(java.util.Collection c)           Adds all of the elements of the given collection to this set (optional operation).
void	clear()           Removes all elements from this set (optional operation).
boolean	contains(java.lang.Object o)           Returns true if the set contains the specified element.
boolean	containsAll(java.util.Collection c)           Returns true if this set contains all elements in the specified collection.
boolean	isEmpty()           Returns true if the set contains no elements.
java.util.Iterator	iterator()           Returns an iterator over the set.
boolean	remove(java.lang.Object o)           Removes the specified element from this set (optional operation).
boolean	removeAll(java.util.Collection c)           Removes from this set all elements in the given collection (optional operation).
boolean	retainAll(java.util.Collection c)           Retains only the elements in this set that are also in the specified collection (optional operation).
int	size()           Returns the number of elements in the set.
java.lang.Object[]	toArray()           Returns an array containing the elements of this set.
java.lang.Object[]	toArray(java.lang.Object[] a)           Returns an array containing the elements of this set, of the same runtime type of the argument.

 

Methods inherited from class java.util.AbstractSet

equals, hashCode

 

Methods inherited from class java.util.AbstractCollection

toString

 

Methods inherited from class java.lang.Object

clone, finalize, getClass, notify, notifyAll, wait, wait, wait

 

Field Detail

al

protected final CopyOnWriteArrayList al

Constructor Detail

CopyOnWriteArraySet

public CopyOnWriteArraySet()

Constructs an empty set

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CopyOnWriteArraySet

public CopyOnWriteArraySet(java.util.Collection c)

Constructs a set containing all of the elements of the specified Collection.

Method Detail

size

public int size()

Description copied from interface: java.util.Set

Returns the number of elements in the set. If there are more than Integer.MAX_VALUE mappings, return Integer.MAX_VALUE. This is the cardinality of the set.

Specified by:

size in interface java.util.Set

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isEmpty

public boolean isEmpty()

Description copied from interface: java.util.Set

Returns true if the set contains no elements.

Specified by:

isEmpty in interface java.util.Set

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contains

public boolean contains(java.lang.Object o)

Description copied from interface: java.util.Set

Returns true if the set contains the specified element. In other words, this looks for o == null ? e == null : o.equals(e).

Specified by:

contains in interface java.util.Set

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toArray

public java.lang.Object[] toArray()

Description copied from interface: java.util.Set

Returns an array containing the elements of this set. If the set makes a guarantee about iteration order, the array has the same order. The array is distinct from the set; modifying one does not affect the other.

Specified by:

toArray in interface java.util.Set

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toArray

public java.lang.Object[] toArray(java.lang.Object[] a)

Description copied from interface: java.util.Set

Returns an array containing the elements of this set, of the same runtime type of the argument. If the given set is large enough, it is reused, and null is inserted in the first unused slot. Otherwise, reflection is used to build a new array. If the set makes a guarantee about iteration order, the array has the same order. The array is distinct from the set; modifying one does not affect the other.

Specified by:

toArray in interface java.util.Set

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clear

public void clear()

Description copied from interface: java.util.Set

Removes all elements from this set (optional operation). This set will be empty afterwords, unless an exception occurs.

Specified by:

clear in interface java.util.Set

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iterator

public java.util.Iterator iterator()

Description copied from interface: java.util.Set

Returns an iterator over the set. The iterator has no specific order, unless further specified.

Specified by:

iterator in interface java.util.Set

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remove

public boolean remove(java.lang.Object o)

Description copied from interface: java.util.Set

Removes the specified element from this set (optional operation). If an element e exists, o == null ? e == null : o.equals(e), it is removed from the set.

Specified by:

remove in interface java.util.Set

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containsAll

public boolean containsAll(java.util.Collection c)

Description copied from interface: java.util.Set

Returns true if this set contains all elements in the specified collection. If the argument is also a set, this is the subset relationship.

Specified by:

containsAll in interface java.util.Set

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addAll

public boolean addAll(java.util.Collection c)

Description copied from interface: java.util.Set

Adds all of the elements of the given collection to this set (optional operation). If the argument is also a Set, this returns the mathematical union of the two. The behavior is unspecified if the set is modified while this is taking place.

Specified by:

addAll in interface java.util.Set

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removeAll

public boolean removeAll(java.util.Collection c)

Description copied from class: java.util.AbstractSet

Removes from this set all elements in the given collection (optional operation). This implementation uses size() to determine the smaller collection. Then, if this set is smaller, it iterates over the set, calling Iterator.remove if the collection contains the element. If this set is larger, it iterates over the collection, calling Set.remove for all elements in the collection. Note that this operation will fail if a remove methods is not supported.

Specified by:

removeAll in interface java.util.Set

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retainAll

public boolean retainAll(java.util.Collection c)

Description copied from interface: java.util.Set

Retains only the elements in this set that are also in the specified collection (optional operation). If the argument is also a set, this performs the intersection of the two sets.

Specified by:

retainAll in interface java.util.Set

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add

public boolean add(java.lang.Object o)

Description copied from interface: java.util.Set

Adds the specified element to the set if it is not already present (optional operation). In particular, the comparison algorithm is o == null ? e == null : o.equals(e). Sets need not permit all values, and may document what exceptions will be thrown if a value is not permitted.

Specified by:

add in interface java.util.Set

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Overview  Package   Class  Use  Deprecated  Index
Home >> All >> org >> ematgine >> utils >> [ concurrent overview ]	PREV CLASS  NEXT CLASS
SUMMARY:  JAVADOC |  SOURCE |  DOWNLOAD | NESTED | FIELD | CONSTR | METHOD	DETAIL: FIELD | CONSTR | METHOD

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