com.oracle.graal.pointsto.util

Class ConcurrentLightHashMap

java.lang.Object

com.oracle.graal.pointsto.util.ConcurrentLightHashMap

public final class ConcurrentLightHashMap
extends Object

Implements a hash map that is concurrent, backed by a concurrent hash map, and memory efficient. The memory efficiency comes from the fact that the underlying map is initialized only when it contains more than one entry. When it contains a single entry it is simply stored in a field as a AbstractMap.SimpleImmutableEntry. When the map is empty the field is null. In situations where is likely that the map will contain no or only one entry 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 entries: the location is set to null
2. One entry: the entry is stored directly in this location as a AbstractMap.SimpleImmutableEntry.
3. Multiple entries: the location points to a ConcurrentHashMap storing the entries

This map doesn't allow null keys or values.

Method Summary

Modifier and Type	Method and Description
static <U> void	clear(U holder, AtomicReferenceFieldUpdater<U,Object> updater)
static <K,V,U> V	computeIfAbsent(U holder, AtomicReferenceFieldUpdater<U,Object> updater, K key, Function<? super K,? extends V> mappingFunction) Sets the key to the value computed by the mapping function if there is no mapping for the key.
static <K,V,U> void	forEach(U holder, AtomicReferenceFieldUpdater<U,Object> updater, BiConsumer<? super K,? super V> action)
static <K,V,U> V	get(U holder, AtomicReferenceFieldUpdater<U,Object> updater, K key)
static <K,V,U> Map<K,V>	getEntries(U holder, AtomicReferenceFieldUpdater<U,Object> updater)
static <K,V,U> V	getOrDefault(U holder, AtomicReferenceFieldUpdater<U,Object> updater, K key, V defaultValue)
static <K,V,U> V	putIfAbsent(U holder, AtomicReferenceFieldUpdater<U,Object> updater, K newKey, V newValue) If the specified key is not already associated with a value, associates it with the given value.
static <K,V,U> boolean	remove(U holder, AtomicReferenceFieldUpdater<U,Object> updater, K key)
static <K,V,U> boolean	removeIf(U holder, AtomicReferenceFieldUpdater<U,Object> updater, Predicate<Map.Entry<K,V>> filter)

Methods inherited from class java.lang.Object

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

Method Detail

putIfAbsent

public static <K,V,U> V putIfAbsent(U holder,
                                    AtomicReferenceFieldUpdater<U,Object> updater,
                                    K newKey,
                                    V newValue)

If the specified key is not already associated with a value, associates it with the given value.

Returns:

the previous value associated with the specified key, or null if there was no mapping for the key.

Throws:

NullPointerException - if the specified key or value is null

computeIfAbsent

public static <K,V,U> V computeIfAbsent(U holder,
                                        AtomicReferenceFieldUpdater<U,Object> updater,
                                        K key,
                                        Function<? super K,? extends V> mappingFunction)

Sets the key to the value computed by the mapping function if there is no mapping for the key. If the mapping function returns null, no mapping is recorded. This doesn't make any guarantees that the mapping function is only executed once.

Returns:

the current (existing or computed) value associated with the specified key, or null if the computed value is null

Throws:

NullPointerException - if the specified key is null, since this map does not support null keys, or the mappingFunction is null

getOrDefault

public static <K,V,U> V getOrDefault(U holder,
                                     AtomicReferenceFieldUpdater<U,Object> updater,
                                     K key,
                                     V defaultValue)

get

public static <K,V,U> V get(U holder,
                            AtomicReferenceFieldUpdater<U,Object> updater,
                            K key)

getEntries

public static <K,V,U> Map<K,V> getEntries(U holder,
                                          AtomicReferenceFieldUpdater<U,Object> updater)

forEach

public static <K,V,U> void forEach(U holder,
                                   AtomicReferenceFieldUpdater<U,Object> updater,
                                   BiConsumer<? super K,? super V> action)

remove

public static <K,V,U> boolean remove(U holder,
                                     AtomicReferenceFieldUpdater<U,Object> updater,
                                     K key)

removeIf

public static <K,V,U> boolean removeIf(U holder,
                                       AtomicReferenceFieldUpdater<U,Object> updater,
                                       Predicate<Map.Entry<K,V>> filter)

clear

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