com.oracle.graal.pointsto.util

Class ConcurrentLightHashSet

java.lang.Object

com.oracle.graal.pointsto.util.ConcurrentLightHashSet

public final class ConcurrentLightHashSet
extends Object

Implements a hash set that is concurrent, backed by a concurrent hash map, and memory efficient. The memory efficiency comes from the fact that the map is initialized only when the set contains more than one element. When it contains a single element it is simply stored in a field. When the set is empty the field is null. In situations where is likely that the set will contain no or only one element there is no memory overhead incurred by allocating the map. The value is not referenced by objects of this class but all operations use a AtomicReferenceFieldUpdater to a storage location of type Object. This location is then populated with three possible values:

1. No elements: the location is set to null
2. One element: the single element is stored directly in this location.
3. Multiple elements: the location points to a ConcurrentHashMap with the elements as the keys. The values of the map are unused.

Method Summary

Modifier and Type	Method and Description
static <T,U> boolean	addElement(U holder, AtomicReferenceFieldUpdater<U,Object> updater, T newElement)
static <U> void	clear(U holder, AtomicReferenceFieldUpdater<U,Object> updater)
static <T,U> Collection<T>	getElements(U holder, AtomicReferenceFieldUpdater<U,Object> updater)
static <T,U> boolean	removeElement(U holder, AtomicReferenceFieldUpdater<U,Object> updater, T element)
static int	size(Object elements)

Methods inherited from class java.lang.Object

clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

Method Detail

size

public static int size(Object elements)

addElement

public static <T,U> boolean addElement(U holder,
                                       AtomicReferenceFieldUpdater<U,Object> updater,
                                       T newElement)

getElements

public static <T,U> Collection<T> getElements(U holder,
                                              AtomicReferenceFieldUpdater<U,Object> updater)

removeElement

public static <T,U> boolean removeElement(U holder,
                                          AtomicReferenceFieldUpdater<U,Object> updater,
                                          T element)

clear

public static <U> void clear(U holder,
                             AtomicReferenceFieldUpdater<U,Object> updater)