java.lang.Object | ||
↳ | java.util.AbstractMap<K, V> | |
↳ | java.util.concurrent.ConcurrentSkipListMap<K, V> |
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.
Public Constructors | |||||||||||
---|---|---|---|---|---|---|---|---|---|---|---|
Constructs a new, empty map, sorted according to the
natural ordering of the keys. | |||||||||||
Constructs a new, empty map, sorted according to the specified
comparator.
| |||||||||||
Constructs a new map containing the same mappings as the given map,
sorted according to the
natural ordering of
the keys. | |||||||||||
Constructs a new map containing the same mappings and using the
same ordering as the specified sorted map.
|
Public Methods | |||||||||||
---|---|---|---|---|---|---|---|---|---|---|---|
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. | |||||||||||
Returns the least key greater than or equal to the given key,
or
null if there is no such key. | |||||||||||
Removes all of the mappings from this map.
| |||||||||||
Returns a shallow copy of this
ConcurrentSkipListMap
instance. | |||||||||||
Returns the comparator used to compare keys in this sorted map, or null if the natural
ordering is in use.
| |||||||||||
Returns
true if this map contains a mapping for the specified
key. | |||||||||||
Returns
true if this map maps one or more keys to the
specified value. | |||||||||||
Returns a reverse order
NavigableSet view of the keys contained in this map. | |||||||||||
Returns a reverse order view of the mappings contained in this map.
| |||||||||||
Returns a
Set view of the mappings contained in this map. | |||||||||||
Compares the specified object with this map for equality.
| |||||||||||
Returns a key-value mapping associated with the least
key in this map, or
null if the map is empty. | |||||||||||
Returns the least key in this sorted map.
| |||||||||||
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. | |||||||||||
Returns the greatest key less than or equal to the given key,
or
null if there is no such key. | |||||||||||
Returns the value to which the specified key is mapped,
or
null if this map contains no mapping for the key. | |||||||||||
Returns a view of the portion of this map whose keys are less than (or
equal to, if
inclusive is true) toKey . | |||||||||||
Returns a sorted map over a range of this sorted map with all keys that
are less than the specified
endKey .
Equivalent to | |||||||||||
Returns a key-value mapping associated with the least key
strictly greater than the given key, or
null if there
is no such key. | |||||||||||
Returns the least key strictly greater than the given key, or
null if there is no such key. | |||||||||||
Returns
true if this map contains no key-value mappings. | |||||||||||
Returns a
NavigableSet view of the keys contained in this map. | |||||||||||
Returns a key-value mapping associated with the greatest
key in this map, or
null if the map is empty. | |||||||||||
Returns the greatest key in this sorted map.
| |||||||||||
Returns a key-value mapping associated with the greatest key
strictly less than the given key, or
null if there is
no such key. | |||||||||||
Returns the greatest key strictly less than the given key, or
null if there is no such key. | |||||||||||
Returns a
NavigableSet view of the keys contained in this map. | |||||||||||
Removes and returns a key-value mapping associated with
the least key in this map, or
null if the map is empty. | |||||||||||
Removes and returns a key-value mapping associated with
the greatest key in this map, or
null if the map is empty. | |||||||||||
Associates the specified value with the specified key in this map.
| |||||||||||
If the specified key is not already associated
with a value, associate it with the given value.
| |||||||||||
Removes the entry for a key only if currently mapped to a given value.
| |||||||||||
Removes the mapping for the specified key from this map if present.
| |||||||||||
Replaces the entry for a key only if currently mapped to a given value.
| |||||||||||
Replaces the entry for a key only if currently mapped to some value.
| |||||||||||
Returns the number of key-value mappings in this map.
| |||||||||||
Returns a sorted map over a range of this sorted map with all keys
greater than or equal to the specified
startKey and less than the
specified endKey .
Equivalent to | |||||||||||
Returns a view of the portion of this map whose keys range from
fromKey to toKey . | |||||||||||
Returns a view of the portion of this map whose keys are greater than (or
equal to, if
inclusive is true) fromKey . | |||||||||||
Returns a sorted map over a range of this sorted map with all keys that
are greater than or equal to the specified
startKey .
Equivalent to | |||||||||||
Returns a
Collection view of the values contained in this map. |
[Expand]
Inherited Methods | |||||||||||
---|---|---|---|---|---|---|---|---|---|---|---|
From class
java.util.AbstractMap
| |||||||||||
From class
java.lang.Object
| |||||||||||
From interface
java.util.Map
| |||||||||||
From interface java.util.NavigableMap | |||||||||||
From interface
java.util.SortedMap
| |||||||||||
From interface
java.util.concurrent.ConcurrentMap
| |||||||||||
From interface java.util.concurrent.ConcurrentNavigableMap |
Constructs a new, empty map, sorted according to the
natural ordering
of the keys.
Constructs a new, empty map, sorted according to the specified comparator.
comparator | the comparator that will be used to order this map.
If null , the natural
ordering of the keys will be used.
|
---|
Constructs a new map containing the same mappings as the given map,
sorted according to the natural ordering
of
the keys.
m | the map whose mappings are to be placed in this map |
---|
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 |
Constructs a new map containing the same mappings and using the same ordering as the specified sorted map.
m | the sorted map whose mappings are to be placed in this map, and whose comparator is to be used to sort this map |
---|
NullPointerException | if the specified sorted map or any of its keys or values are null |
---|
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.
key | the key |
---|
key
, or null
if there is no such keyClassCastException | |
---|---|
NullPointerException | if the specified key is null |
Returns the least key greater than or equal to the given key,
or null
if there is no such key.
key | the key |
---|
key
,
or null
if there is no such keyClassCastException | |
---|---|
NullPointerException | if the specified key is null |
Returns a shallow copy of this ConcurrentSkipListMap
instance. (The keys and values themselves are not cloned.)
Returns the comparator used to compare keys in this sorted map, or null if the natural ordering is in use.
Returns true
if this map contains a mapping for the specified
key.
key | key whose presence in this map is to be tested |
---|
true
if this map contains a mapping for the specified keyClassCastException | if the specified key cannot be compared with the keys currently in the map |
---|---|
NullPointerException | if the specified key is null |
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.
value | value whose presence in this map is to be tested |
---|
true
if a mapping to value
exists;
false
otherwiseNullPointerException | if the specified value is null |
---|
Returns a reverse order NavigableSet
view of the keys contained in this map.
The set's iterator returns the keys in descending 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.
Returns a reverse order view of the mappings contained in this map. The descending map is backed by this map, so changes to the map are reflected in the descending map, and vice-versa.
The returned map has an ordering equivalent to
Collections.reverseOrder
(comparator())
.
The expression m.descendingMap().descendingMap()
returns a
view of m
essentially equivalent to m
.
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.
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.
o | object to be compared for equality with this map |
---|
true
if the specified object is equal to this map
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.
Returns the least key in this sorted map.
NoSuchElementException |
---|
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.
key | the key |
---|
key
, or null
if there is no such keyClassCastException | |
---|---|
NullPointerException | if the specified key is null |
Returns the greatest key less than or equal to the given key,
or null
if there is no such key.
key | the key |
---|
key
,
or null
if there is no such keyClassCastException | |
---|---|
NullPointerException | if the specified key is null |
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.)
key | the key. |
---|
null
if no mapping for the specified key is found.
ClassCastException | if the specified key cannot be compared with the keys currently in the map |
---|---|
NullPointerException | if the specified key is null |
Returns a view of the portion of this map whose keys are less than (or
equal to, if inclusive
is true) toKey
. The returned
map is backed by this map, so changes in the returned map are reflected
in this map, and vice-versa. The returned map supports all optional
map operations that this map supports.
The returned map will throw an IllegalArgumentException
on an attempt to insert a key outside its range.
toKey | high endpoint of the keys in the returned map |
---|---|
inclusive | true if the high endpoint
is to be included in the returned view |
inclusive
is true) toKey
ClassCastException | |
---|---|
NullPointerException | if toKey is null |
IllegalArgumentException |
Returns a sorted map over a range of this sorted map with all keys that
are less than the specified endKey
. Changes to the returned
sorted map are reflected in this sorted map and vice versa.
Note: The returned map will not allow an insertion of a key outside the specified range.
Equivalent to headMap(toKey, false)
.
toKey | the high boundary of the range specified. |
---|
endKey
.ClassCastException | |
---|---|
NullPointerException | if toKey is null |
IllegalArgumentException |
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.
key | the key |
---|
key
,
or null
if there is no such keyClassCastException | |
---|---|
NullPointerException | if the specified key is null |
Returns the least key strictly greater than the given key, or
null
if there is no such key.
key | the key |
---|
key
,
or null
if there is no such keyClassCastException | |
---|---|
NullPointerException | if the specified key is null |
Returns true
if this map contains no key-value mappings.
true
if this map contains no key-value mappings
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
.
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.
Returns the greatest key in this sorted map.
NoSuchElementException |
---|
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.
key | the key |
---|
key
,
or null
if there is no such keyClassCastException | |
---|---|
NullPointerException | if the specified key is null |
Returns the greatest key strictly less than the given key, or
null
if there is no such key.
key | the key |
---|
key
,
or null
if there is no such keyClassCastException | |
---|---|
NullPointerException | if the specified key is null |
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.
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.
null
if this map is empty
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.
null
if this map is empty
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.
key | key with which the specified value is to be associated |
---|---|
value | value to be associated with the specified key |
null
if there was no mapping for the keyClassCastException | if the specified key cannot be compared with the keys currently in the map |
---|---|
NullPointerException | if the specified key or value is null |
If the specified key is not already associated with a value, associate it with the given value. This is equivalent to
if (!map.containsKey(key))
return map.put(key, value);
else
return map.get(key);
except that the action is performed atomically.key | key with which the specified value is to be associated |
---|---|
value | value to be associated with the specified key |
null
if there was no mapping for the keyClassCastException | if the specified key cannot be compared with the keys currently in the map |
---|---|
NullPointerException | if the specified key or value is null |
Removes the entry for a key only if currently mapped to a given value. This is equivalent to
if (map.containsKey(key) && map.get(key).equals(value)) {
map.remove(key);
return true;
else
return false;}
except that the action is performed atomically.key | key with which the specified value is associated |
---|---|
value | value expected to be associated with the specified key |
true
if the value was removedClassCastException | if the specified key cannot be compared with the keys currently in the map |
---|---|
NullPointerException | if the specified key is null |
Removes the mapping for the specified key from this map if present.
key | key for which mapping should be removed |
---|
null
if there was no mapping for the keyClassCastException | if the specified key cannot be compared with the keys currently in the map |
---|---|
NullPointerException | if the specified key is null |
Replaces the entry for a key only if currently mapped to a given value. This is equivalent to
if (map.containsKey(key) && map.get(key).equals(oldValue)) {
map.put(key, newValue);
return true;
else
return false;}
except that the action is performed atomically.key | key with which the specified value is associated |
---|---|
oldValue | value expected to be associated with the specified key |
newValue | value to be associated with the specified key |
true
if the value was replacedClassCastException | if the specified key cannot be compared with the keys currently in the map |
---|---|
NullPointerException | if any of the arguments are null |
Replaces the entry for a key only if currently mapped to some value. This is equivalent to
if (map.containsKey(key)) {
return map.put(key, value);
else
return null;}
except that the action is performed atomically.key | key with which the specified value is associated |
---|---|
value | value to be associated with the specified key |
null
if there was no mapping for the keyClassCastException | if the specified key cannot be compared with the keys currently in the map |
---|---|
NullPointerException | if the specified key or value is null |
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.
Returns a sorted map over a range of this sorted map with all keys
greater than or equal to the specified startKey
and less than the
specified endKey
. Changes to the returned sorted map are
reflected in this sorted map and vice versa.
Note: The returned map will not allow an insertion of a key outside the specified range.
Equivalent to subMap(fromKey, true, toKey, false)
.
fromKey | the low boundary of the range (inclusive). |
---|---|
toKey | the high boundary of the range (exclusive), |
ClassCastException | |
---|---|
NullPointerException | if fromKey or toKey is null |
IllegalArgumentException |
Returns a view of the portion of this map whose keys range from
fromKey
to toKey
. If fromKey
and
toKey
are equal, the returned map is empty unless
fromExclusive
and toExclusive
are both true. The
returned map is backed by this map, so changes in the returned map are
reflected in this map, and vice-versa. The returned map supports all
optional map operations that this map supports.
The returned map will throw an IllegalArgumentException
on an attempt to insert a key outside of its range, or to construct a
submap either of whose endpoints lie outside its range.
fromKey | low endpoint of the keys in the returned map |
---|---|
fromInclusive | true if the low endpoint
is to be included in the returned view |
toKey | high endpoint of the keys in the returned map |
toInclusive | true if the high endpoint
is to be included in the returned view |
fromKey
to toKey
ClassCastException | |
---|---|
NullPointerException | if fromKey or toKey is null |
IllegalArgumentException |
Returns a view of the portion of this map whose keys are greater than (or
equal to, if inclusive
is true) fromKey
. The returned
map is backed by this map, so changes in the returned map are reflected
in this map, and vice-versa. The returned map supports all optional
map operations that this map supports.
The returned map will throw an IllegalArgumentException
on an attempt to insert a key outside its range.
fromKey | low endpoint of the keys in the returned map |
---|---|
inclusive | true if the low endpoint
is to be included in the returned view |
inclusive
is true) fromKey
ClassCastException | |
---|---|
NullPointerException | if fromKey is null |
IllegalArgumentException |
Returns a sorted map over a range of this sorted map with all keys that
are greater than or equal to the specified startKey
. Changes to
the returned sorted map are reflected in this sorted map and vice versa.
Note: The returned map will not allow an insertion of a key outside the specified range.
Equivalent to tailMap(fromKey, true)
.
fromKey | the low boundary of the range specified. |
---|
startKey
.ClassCastException | |
---|---|
NullPointerException | if fromKey is null |
IllegalArgumentException |
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.