com.gigaspaces.internal.backport.java.util.concurrent

Class FastConcurrentSkipListMap<K,V>

java.lang.Object

java.util.AbstractMap<K,V>

com.gigaspaces.internal.backport.java.util.concurrent.FastConcurrentSkipListMap<K,V>

Type Parameters:

K - the type of keys maintained by this map

V - the type of mapped values

All Implemented Interfaces:

Serializable, Cloneable, ConcurrentMap<K,V>, ConcurrentNavigableMap<K,V>, Map<K,V>, NavigableMap<K,V>, SortedMap<K,V>

public class FastConcurrentSkipListMap<K,V>
extends AbstractMap<K,V>
implements ConcurrentNavigableMap<K,V>, Cloneable, Serializable

A scalable concurrent ConcurrentNavigableMap implementation. The map is sorted according to the natural ordering of its keys, or by a Comparator provided at map creation time, depending on which constructor is used.

This class implements a concurrent variant of SkipLists providing expected average log(n) time cost for the containsKey, get, put and remove operations and their variants. Insertion, removal, update, and access operations safely execute concurrently by multiple threads. Iterators are weakly consistent, returning elements reflecting the state of the map at some point at or since the creation of the iterator. They do not throw ConcurrentModificationException, and may proceed concurrently with other operations. Ascending key ordered views and their iterators are faster than descending ones.

All Map.Entry pairs returned by methods in this class and its views represent snapshots of mappings at the time they were produced. They do not support the Entry.setValue method. (Note however that it is possible to change mappings in the associated map using put, putIfAbsent, or replace, depending on exactly which effect you need.)

Beware that, unlike in most collections, the size method is not a constant-time operation. Because of the asynchronous nature of these maps, determining the current number of elements requires a traversal of the elements, and so may report inaccurate results if this collection is modified during traversal. Additionally, the bulk operations putAll, equals, toArray, containsValue, and clear are not guaranteed to be performed atomically. For example, an iterator operating concurrently with a putAll operation might view only some of the added elements.

This class and its views and iterators implement all of the optional methods of the Map and Iterator interfaces. Like most other concurrent collections, this class does not permit the use of null keys or values because some null return values cannot be reliably distinguished from the absence of elements.

This class is a member of the Java Collections Framework.

Since:

1.6

Author:

Doug Lea

See Also:

Serialized Form

Nested Class Summary

Nested classes/interfaces inherited from class java.util.AbstractMap

AbstractMap.SimpleEntry<K,V>, AbstractMap.SimpleImmutableEntry<K,V>

Nested classes/interfaces inherited from interface java.util.Map

Map.Entry<K,V>

Constructor Summary

Constructors

Constructor and Description
FastConcurrentSkipListMap() Constructs a new, empty map, sorted according to the natural ordering of the keys.
FastConcurrentSkipListMap(Comparator<? super K> comparator) Constructs a new, empty map, sorted according to the specified comparator.
FastConcurrentSkipListMap(Map<? extends K,? extends V> m) Constructs a new map containing the same mappings as the given map, sorted according to the natural ordering of the keys.
FastConcurrentSkipListMap(SortedMap<K,? extends V> m) Constructs a new map containing the same mappings and using the same ordering as the specified sorted map.

Method Summary

Modifier and Type	Method and Description
Map.Entry<K,V>	ceilingEntry(K key) Returns a key-value mapping associated with the least key greater than or equal to the given key, or null if there is no such entry.
K	ceilingKey(K key)
void	clear() Removes all of the mappings from this map.
FastConcurrentSkipListMap<K,V>	clone() Returns a shallow copy of this ConcurrentSkipListMap instance.
Comparator<? super K>	comparator()
boolean	containsKey(Object key) Returns true if this map contains a mapping for the specified key.
boolean	containsValue(Object value) Returns true if this map maps one or more keys to the specified value.
NavigableSet<K>	descendingKeySet()
ConcurrentNavigableMap<K,V>	descendingMap()
Set<Map.Entry<K,V>>	entrySet() Returns a Set view of the mappings contained in this map.
boolean	equals(Object o) Compares the specified object with this map for equality.
Map.Entry<K,V>	firstEntry() Returns a key-value mapping associated with the least key in this map, or null if the map is empty.
K	firstKey()
Map.Entry<K,V>	floorEntry(K key) Returns a key-value mapping associated with the greatest key less than or equal to the given key, or null if there is no such key.
K	floorKey(K key)
V	get(Object key) Returns the value to which the specified key is mapped, or null if this map contains no mapping for the key.
ConcurrentNavigableMap<K,V>	headMap(K toKey)
ConcurrentNavigableMap<K,V>	headMap(K toKey, boolean inclusive)
Map.Entry<K,V>	higherEntry(K key) Returns a key-value mapping associated with the least key strictly greater than the given key, or null if there is no such key.
K	higherKey(K key)
boolean	isEmpty() Returns true if this map contains no key-value mappings.
NavigableSet<K>	keySet() Returns a NavigableSet view of the keys contained in this map.
Map.Entry<K,V>	lastEntry() Returns a key-value mapping associated with the greatest key in this map, or null if the map is empty.
K	lastKey()
Map.Entry<K,V>	lowerEntry(K key) Returns a key-value mapping associated with the greatest key strictly less than the given key, or null if there is no such key.
K	lowerKey(K key)
NavigableSet<K>	navigableKeySet()
Map.Entry<K,V>	pollFirstEntry() Removes and returns a key-value mapping associated with the least key in this map, or null if the map is empty.
Map.Entry<K,V>	pollLastEntry() Removes and returns a key-value mapping associated with the greatest key in this map, or null if the map is empty.
V	put(K key, V value) Associates the specified value with the specified key in this map.
V	putIfAbsent(K key, V value)
V	remove(Object key) Removes the mapping for the specified key from this map if present.
boolean	remove(Object key, Object value)
V	replace(K key, V value)
boolean	replace(K key, V oldValue, V newValue)
int	size() Returns the number of key-value mappings in this map.
ConcurrentNavigableMap<K,V>	subMap(K fromKey, boolean fromInclusive, K toKey, boolean toInclusive)
ConcurrentNavigableMap<K,V>	subMap(K fromKey, K toKey)
ConcurrentNavigableMap<K,V>	tailMap(K fromKey)
ConcurrentNavigableMap<K,V>	tailMap(K fromKey, boolean inclusive)
Collection<V>	values() Returns a Collection view of the values contained in this map.

Methods inherited from class java.util.AbstractMap

hashCode, putAll, toString

Methods inherited from class java.lang.Object

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

Methods inherited from interface java.util.concurrent.ConcurrentMap

compute, computeIfAbsent, computeIfPresent, forEach, getOrDefault, merge, replaceAll

Methods inherited from interface java.util.Map

hashCode, putAll

Constructor Detail

FastConcurrentSkipListMap

public FastConcurrentSkipListMap()

Constructs a new, empty map, sorted according to the natural ordering of the keys.

FastConcurrentSkipListMap

public FastConcurrentSkipListMap(Comparator<? super K> comparator)

Constructs a new, empty map, sorted according to the specified comparator.

Parameters:

comparator - the comparator that will be used to order this map. If null, the natural ordering of the keys will be used.

FastConcurrentSkipListMap

public FastConcurrentSkipListMap(Map<? extends K,? extends V> m)

Constructs a new map containing the same mappings as the given map, sorted according to the natural ordering of the keys.

Parameters:

m - the map whose mappings are to be placed in this map

Throws:

ClassCastException - if the keys in m are not Comparable, or are not mutually comparable

NullPointerException - if the specified map or any of its keys or values are null

FastConcurrentSkipListMap

public FastConcurrentSkipListMap(SortedMap<K,? extends V> m)

Constructs a new map containing the same mappings and using the same ordering as the specified sorted map.

Parameters:

m - the sorted map whose mappings are to be placed in this map, and whose comparator is to be used to sort this map

Throws:

NullPointerException - if the specified sorted map or any of its keys or values are null

Method Detail

clone

public FastConcurrentSkipListMap<K,V> clone()

Returns a shallow copy of this ConcurrentSkipListMap instance. (The keys and values themselves are not cloned.)

Overrides:

clone in class AbstractMap<K,V>

Returns:

a shallow copy of this map

containsKey

public boolean containsKey(Object key)

Returns true if this map contains a mapping for the specified key.

Specified by:

containsKey in interface Map<K,V>

Overrides:

containsKey in class AbstractMap<K,V>

Parameters:

key - key whose presence in this map is to be tested

Returns:

true if this map contains a mapping for the specified key

Throws:

ClassCastException - if the specified key cannot be compared with the keys currently in the map

NullPointerException - if the specified key is null

get

public V get(Object key)

Returns the value to which the specified key is mapped, or null if this map contains no mapping for the key.

More formally, if this map contains a mapping from a key k to a value v such that key compares equal to k according to the map's ordering, then this method returns v; otherwise it returns null. (There can be at most one such mapping.)

Specified by:

get in interface Map<K,V>

Overrides:

get in class AbstractMap<K,V>

Throws:

ClassCastException - if the specified key cannot be compared with the keys currently in the map

NullPointerException - if the specified key is null

put

public V put(K key,
             V value)

Associates the specified value with the specified key in this map. If the map previously contained a mapping for the key, the old value is replaced.

Specified by:

put in interface Map<K,V>

Overrides:

put in class AbstractMap<K,V>

Parameters:

key - key with which the specified value is to be associated

value - value to be associated with the specified key

Returns:

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

Throws:

ClassCastException - if the specified key cannot be compared with the keys currently in the map

NullPointerException - if the specified key or value is null

remove

public V remove(Object key)

Removes the mapping for the specified key from this map if present.

Specified by:

remove in interface Map<K,V>

Overrides:

remove in class AbstractMap<K,V>

Parameters:

key - key for which mapping should be removed

Returns:

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

Throws:

ClassCastException - if the specified key cannot be compared with the keys currently in the map

NullPointerException - if the specified key is null

containsValue

public boolean containsValue(Object value)

Returns true if this map maps one or more keys to the specified value. This operation requires time linear in the map size. Additionally, it is possible for the map to change during execution of this method, in which case the returned result may be inaccurate.

Specified by:

containsValue in interface Map<K,V>

Overrides:

containsValue in class AbstractMap<K,V>

Parameters:

value - value whose presence in this map is to be tested

Returns:

true if a mapping to value exists; false otherwise

Throws:

NullPointerException - if the specified value is null

size

public int size()

Returns the number of key-value mappings in this map. If this map contains more than Integer.MAX_VALUE elements, it returns Integer.MAX_VALUE.

Beware that, unlike in most collections, this method is NOT a constant-time operation. Because of the asynchronous nature of these maps, determining the current number of elements requires traversing them all to count them. Additionally, it is possible for the size to change during execution of this method, in which case the returned result will be inaccurate. Thus, this method is typically not very useful in concurrent applications.

Specified by:

size in interface Map<K,V>

Overrides:

size in class AbstractMap<K,V>

Returns:

the number of elements in this map

isEmpty

public boolean isEmpty()

Returns true if this map contains no key-value mappings.

Specified by:

isEmpty in interface Map<K,V>

Overrides:

isEmpty in class AbstractMap<K,V>

Returns:

true if this map contains no key-value mappings

clear

public void clear()

Removes all of the mappings from this map.

Specified by:

clear in interface Map<K,V>

Overrides:

clear in class AbstractMap<K,V>

keySet

public NavigableSet<K> keySet()

Returns a NavigableSet view of the keys contained in this map. The set's iterator returns the keys in ascending order. The set is backed by the map, so changes to the map are reflected in the set, and vice-versa. The set supports element removal, which removes the corresponding mapping from the map, via the Iterator.remove, Set.remove, removeAll, retainAll, and clear operations. It does not support the add or addAll operations.

The view's iterator is a "weakly consistent" iterator that will never throw ConcurrentModificationException, and guarantees to traverse elements as they existed upon construction of the iterator, and may (but is not guaranteed to) reflect any modifications subsequent to construction.

This method is equivalent to method navigableKeySet.

Specified by:

keySet in interface ConcurrentNavigableMap<K,V>

Specified by:

keySet in interface Map<K,V>

Specified by:

keySet in interface SortedMap<K,V>

Overrides:

keySet in class AbstractMap<K,V>

Returns:

a navigable set view of the keys in this map

navigableKeySet

public NavigableSet<K> navigableKeySet()

Specified by:

navigableKeySet in interface ConcurrentNavigableMap<K,V>

Specified by:

navigableKeySet in interface NavigableMap<K,V>

values

public Collection<V> values()

Returns a Collection view of the values contained in this map. The collection's iterator returns the values in ascending order of the corresponding keys. The collection is backed by the map, so changes to the map are reflected in the collection, and vice-versa. The collection supports element removal, which removes the corresponding mapping from the map, via the Iterator.remove, Collection.remove, removeAll, retainAll and clear operations. It does not support the add or addAll operations.

The view's iterator is a "weakly consistent" iterator that will never throw ConcurrentModificationException, and guarantees to traverse elements as they existed upon construction of the iterator, and may (but is not guaranteed to) reflect any modifications subsequent to construction.

Specified by:

values in interface Map<K,V>

Specified by:

values in interface SortedMap<K,V>

Overrides:

values in class AbstractMap<K,V>

entrySet

public Set<Map.Entry<K,V>> entrySet()

Returns a Set view of the mappings contained in this map. The set's iterator returns the entries in ascending key order. The set is backed by the map, so changes to the map are reflected in the set, and vice-versa. The set supports element removal, which removes the corresponding mapping from the map, via the Iterator.remove, Set.remove, removeAll, retainAll and clear operations. It does not support the add or addAll operations.

The view's iterator is a "weakly consistent" iterator that will never throw ConcurrentModificationException, and guarantees to traverse elements as they existed upon construction of the iterator, and may (but is not guaranteed to) reflect any modifications subsequent to construction.

The Map.Entry elements returned by iterator.next() do not support the setValue operation.

Specified by:

entrySet in interface Map<K,V>

Specified by:

entrySet in interface SortedMap<K,V>

Specified by:

entrySet in class AbstractMap<K,V>

Returns:

a set view of the mappings contained in this map, sorted in ascending key order

descendingMap

public ConcurrentNavigableMap<K,V> descendingMap()

Specified by:

descendingMap in interface ConcurrentNavigableMap<K,V>

Specified by:

descendingMap in interface NavigableMap<K,V>

descendingKeySet

public NavigableSet<K> descendingKeySet()

Specified by:

descendingKeySet in interface ConcurrentNavigableMap<K,V>

Specified by:

descendingKeySet in interface NavigableMap<K,V>

equals

public boolean equals(Object o)

Compares the specified object with this map for equality. Returns true if the given object is also a map and the two maps represent the same mappings. More formally, two maps m1 and m2 represent the same mappings if m1.entrySet().equals(m2.entrySet()). This operation may return misleading results if either map is concurrently modified during execution of this method.

Specified by:

equals in interface Map<K,V>

Overrides:

equals in class AbstractMap<K,V>

Parameters:

o - object to be compared for equality with this map

Returns:

true if the specified object is equal to this map

putIfAbsent

public V putIfAbsent(K key,
                     V value)

Specified by:

putIfAbsent in interface ConcurrentMap<K,V>

Specified by:

putIfAbsent in interface Map<K,V>

Returns:

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

Throws:

ClassCastException - if the specified key cannot be compared with the keys currently in the map

NullPointerException - if the specified key or value is null

remove

public boolean remove(Object key,
                      Object value)

Specified by:

remove in interface ConcurrentMap<K,V>

Specified by:

remove in interface Map<K,V>

Throws:

ClassCastException - if the specified key cannot be compared with the keys currently in the map

NullPointerException - if the specified key is null

replace

public boolean replace(K key,
                       V oldValue,
                       V newValue)

Specified by:

replace in interface ConcurrentMap<K,V>

Specified by:

replace in interface Map<K,V>

Throws:

ClassCastException - if the specified key cannot be compared with the keys currently in the map

NullPointerException - if any of the arguments are null

replace

public V replace(K key,
                 V value)

Specified by:

replace in interface ConcurrentMap<K,V>

Specified by:

replace in interface Map<K,V>

Returns:

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

Throws:

ClassCastException - if the specified key cannot be compared with the keys currently in the map

NullPointerException - if the specified key or value is null

comparator

public Comparator<? super K> comparator()

Specified by:

comparator in interface SortedMap<K,V>

firstKey

public K firstKey()

Specified by:

firstKey in interface SortedMap<K,V>

Throws:

NoSuchElementException

lastKey

public K lastKey()

Specified by:

lastKey in interface SortedMap<K,V>

Throws:

NoSuchElementException

subMap

public ConcurrentNavigableMap<K,V> subMap(K fromKey,
                                          boolean fromInclusive,
                                          K toKey,
                                          boolean toInclusive)

Specified by:

subMap in interface ConcurrentNavigableMap<K,V>

Specified by:

subMap in interface NavigableMap<K,V>

Throws:

ClassCastException

NullPointerException - if fromKey or toKey is null

IllegalArgumentException

headMap

public ConcurrentNavigableMap<K,V> headMap(K toKey,
                                           boolean inclusive)

Specified by:

headMap in interface ConcurrentNavigableMap<K,V>

Specified by:

headMap in interface NavigableMap<K,V>

Throws:

ClassCastException

NullPointerException - if toKey is null

IllegalArgumentException

tailMap

public ConcurrentNavigableMap<K,V> tailMap(K fromKey,
                                           boolean inclusive)

Specified by:

tailMap in interface ConcurrentNavigableMap<K,V>

Specified by:

tailMap in interface NavigableMap<K,V>

Throws:

ClassCastException

NullPointerException - if fromKey is null

IllegalArgumentException

subMap

public ConcurrentNavigableMap<K,V> subMap(K fromKey,
                                          K toKey)

Specified by:

subMap in interface ConcurrentNavigableMap<K,V>

Specified by:

subMap in interface NavigableMap<K,V>

Specified by:

subMap in interface SortedMap<K,V>

Throws:

ClassCastException

NullPointerException - if fromKey or toKey is null

IllegalArgumentException

headMap

public ConcurrentNavigableMap<K,V> headMap(K toKey)

Specified by:

headMap in interface ConcurrentNavigableMap<K,V>

Specified by:

headMap in interface NavigableMap<K,V>

Specified by:

headMap in interface SortedMap<K,V>

Throws:

ClassCastException

NullPointerException - if toKey is null

IllegalArgumentException

tailMap

public ConcurrentNavigableMap<K,V> tailMap(K fromKey)

Specified by:

tailMap in interface ConcurrentNavigableMap<K,V>

Specified by:

tailMap in interface NavigableMap<K,V>

Specified by:

tailMap in interface SortedMap<K,V>

Throws:

ClassCastException

NullPointerException - if fromKey is null

IllegalArgumentException

lowerEntry

public Map.Entry<K,V> lowerEntry(K key)

Returns a key-value mapping associated with the greatest key strictly less than the given key, or null if there is no such key. The returned entry does not support the Entry.setValue method.

Specified by:

lowerEntry in interface NavigableMap<K,V>

Throws:

ClassCastException

NullPointerException - if the specified key is null

lowerKey

public K lowerKey(K key)

Specified by:

lowerKey in interface NavigableMap<K,V>

Throws:

ClassCastException

NullPointerException - if the specified key is null

floorEntry

public Map.Entry<K,V> floorEntry(K key)

Returns a key-value mapping associated with the greatest key less than or equal to the given key, or null if there is no such key. The returned entry does not support the Entry.setValue method.

Specified by:

floorEntry in interface NavigableMap<K,V>

Parameters:

key - the key

Throws:

ClassCastException

NullPointerException - if the specified key is null

floorKey

public K floorKey(K key)

Specified by:

floorKey in interface NavigableMap<K,V>

Parameters:

key - the key

Throws:

ClassCastException

NullPointerException - if the specified key is null

ceilingEntry

public Map.Entry<K,V> ceilingEntry(K key)

Returns a key-value mapping associated with the least key greater than or equal to the given key, or null if there is no such entry. The returned entry does not support the Entry.setValue method.

Specified by:

ceilingEntry in interface NavigableMap<K,V>

Throws:

ClassCastException

NullPointerException - if the specified key is null

ceilingKey

public K ceilingKey(K key)

Specified by:

ceilingKey in interface NavigableMap<K,V>

Throws:

ClassCastException

NullPointerException - if the specified key is null

higherEntry

public Map.Entry<K,V> higherEntry(K key)

Returns a key-value mapping associated with the least key strictly greater than the given key, or null if there is no such key. The returned entry does not support the Entry.setValue method.

Specified by:

higherEntry in interface NavigableMap<K,V>

Parameters:

key - the key

Throws:

ClassCastException

NullPointerException - if the specified key is null

higherKey

public K higherKey(K key)

Specified by:

higherKey in interface NavigableMap<K,V>

Parameters:

key - the key

Throws:

ClassCastException

NullPointerException - if the specified key is null

firstEntry

public Map.Entry<K,V> firstEntry()

Returns a key-value mapping associated with the least key in this map, or null if the map is empty. The returned entry does not support the Entry.setValue method.

Specified by:

firstEntry in interface NavigableMap<K,V>

lastEntry

public Map.Entry<K,V> lastEntry()

Returns a key-value mapping associated with the greatest key in this map, or null if the map is empty. The returned entry does not support the Entry.setValue method.

Specified by:

lastEntry in interface NavigableMap<K,V>

pollFirstEntry

public Map.Entry<K,V> pollFirstEntry()

Removes and returns a key-value mapping associated with the least key in this map, or null if the map is empty. The returned entry does not support the Entry.setValue method.

Specified by:

pollFirstEntry in interface NavigableMap<K,V>

pollLastEntry

public Map.Entry<K,V> pollLastEntry()

Removes and returns a key-value mapping associated with the greatest key in this map, or null if the map is empty. The returned entry does not support the Entry.setValue method.

Specified by:

pollLastEntry in interface NavigableMap<K,V>