@GwtCompatible public final class AtomicLongMap<K> extends Object implements Serializable
long
values that can be atomically updated. While writes to a
traditional Map
rely on put(K, V)
, the typical mechanism for writing to this map
is addAndGet(K, long)
, which adds a long
to the value currently associated with
K
. If a key has not yet been associated with a value, its implicit value is zero.
Most methods in this class treat absent values and zero values identically, as individually
documented. Exceptions to this are containsKey(java.lang.Object)
, size()
, isEmpty()
, asMap
, and toString()
.
Instances of this class may be used by multiple threads concurrently. All operations are atomic unless otherwise noted.
Note: If your values are always positive and less than 2^31, you may wish to use a
Multiset
such as ConcurrentHashMultiset
instead.
Warning: Unlike Multiset
, entries whose values are zero are not automatically
removed from the map. Instead they must be removed manually with removeAllZeros()
.
Modifier and Type | Method and Description |
---|---|
long |
accumulateAndGet(K key,
long x,
LongBinaryOperator accumulatorFunction)
Updates the value currently associated with
key by combining it with x via the
specified accumulator function, returning the new value. |
long |
addAndGet(K key,
long delta)
Adds
delta to the value currently associated with key , and returns the new
value. |
Map<K,Long> |
asMap()
Returns a live, read-only view of the map backing this
AtomicLongMap . |
void |
clear()
Removes all of the mappings from this map.
|
boolean |
containsKey(Object key)
Returns true if this map contains a mapping for the specified key.
|
static <K> AtomicLongMap<K> |
create()
Creates an
AtomicLongMap . |
static <K> AtomicLongMap<K> |
create(Map<? extends K,? extends Long> m)
Creates an
AtomicLongMap with the same mappings as the specified Map . |
long |
decrementAndGet(K key)
Decrements by one the value currently associated with
key , and returns the new value. |
long |
get(K key)
Returns the value associated with
key , or zero if there is no value associated with
key . |
long |
getAndAccumulate(K key,
long x,
LongBinaryOperator accumulatorFunction)
Updates the value currently associated with
key by combining it with x via the
specified accumulator function, returning the old value. |
long |
getAndAdd(K key,
long delta)
Adds
delta to the value currently associated with key , and returns the old
value. |
long |
getAndDecrement(K key)
Decrements by one the value currently associated with
key , and returns the old value. |
long |
getAndIncrement(K key)
Increments by one the value currently associated with
key , and returns the old value. |
long |
getAndUpdate(K key,
LongUnaryOperator updaterFunction)
Updates the value currently associated with
key with the specified function, and
returns the old value. |
long |
incrementAndGet(K key)
Increments by one the value currently associated with
key , and returns the new value. |
boolean |
isEmpty()
Returns
true if this map contains no key-value mappings. |
long |
put(K key,
long newValue)
Associates
newValue with key in this map, and returns the value previously
associated with key , or zero if there was no such value. |
void |
putAll(Map<? extends K,? extends Long> m)
Copies all of the mappings from the specified map to this map.
|
long |
remove(K key)
Removes and returns the value associated with
key . |
void |
removeAllZeros()
Removes all mappings from this map whose values are zero.
|
boolean |
removeIfZero(K key)
Atomically remove
key from the map iff its associated value is 0. |
int |
size()
Returns the number of key-value mappings in this map.
|
long |
sum()
Returns the sum of all values in this map.
|
String |
toString()
Returns a string representation of the object.
|
long |
updateAndGet(K key,
LongUnaryOperator updaterFunction)
Updates the value currently associated with
key with the specified function, and
returns the new value. |
public static <K> AtomicLongMap<K> create()
AtomicLongMap
.public static <K> AtomicLongMap<K> create(Map<? extends K,? extends Long> m)
AtomicLongMap
with the same mappings as the specified Map
.public long get(K key)
key
, or zero if there is no value associated with
key
.@CanIgnoreReturnValue public long incrementAndGet(K key)
key
, and returns the new value.@CanIgnoreReturnValue public long decrementAndGet(K key)
key
, and returns the new value.@CanIgnoreReturnValue public long addAndGet(K key, long delta)
delta
to the value currently associated with key
, and returns the new
value.@CanIgnoreReturnValue public long getAndIncrement(K key)
key
, and returns the old value.@CanIgnoreReturnValue public long getAndDecrement(K key)
key
, and returns the old value.@CanIgnoreReturnValue public long getAndAdd(K key, long delta)
delta
to the value currently associated with key
, and returns the old
value.@CanIgnoreReturnValue public long updateAndGet(K key, LongUnaryOperator updaterFunction)
key
with the specified function, and
returns the new value. If there is not currently a value associated with key
, the
function is applied to 0L
.@CanIgnoreReturnValue public long getAndUpdate(K key, LongUnaryOperator updaterFunction)
key
with the specified function, and
returns the old value. If there is not currently a value associated with key
, the
function is applied to 0L
.@CanIgnoreReturnValue public long accumulateAndGet(K key, long x, LongBinaryOperator accumulatorFunction)
key
by combining it with x
via the
specified accumulator function, returning the new value. The previous value associated with
key
(or zero, if there is none) is passed as the first argument to accumulatorFunction
, and x
is passed as the second argument.@CanIgnoreReturnValue public long getAndAccumulate(K key, long x, LongBinaryOperator accumulatorFunction)
key
by combining it with x
via the
specified accumulator function, returning the old value. The previous value associated with
key
(or zero, if there is none) is passed as the first argument to accumulatorFunction
, and x
is passed as the second argument.@CanIgnoreReturnValue public long put(K key, long newValue)
newValue
with key
in this map, and returns the value previously
associated with key
, or zero if there was no such value.public void putAll(Map<? extends K,? extends Long> m)
put(k, v)
on this map once for each mapping from key
k
to value v
in the specified map. The behavior of this operation is undefined
if the specified map is modified while the operation is in progress.@CanIgnoreReturnValue public long remove(K key)
key
. If key
is not in the map,
this method has no effect and returns zero.@Beta @CanIgnoreReturnValue public boolean removeIfZero(K key)
key
from the map iff its associated value is 0.public void removeAllZeros()
This method is not atomic: the map may be visible in intermediate states, where some of the zero values have been removed and others have not.
public long sum()
This method is not atomic: the sum may or may not include other concurrent operations.
public Map<K,Long> asMap()
AtomicLongMap
.public boolean containsKey(Object key)
public int size()
Integer.MAX_VALUE
elements, returns Integer.MAX_VALUE
.public boolean isEmpty()
true
if this map contains no key-value mappings.public void clear()
This method is not atomic: the map may not be empty after returning if there were concurrent writes.
public String toString()
java.lang.Object
toString
method returns a string that
"textually represents" this object. The result should
be a concise but informative representation that is easy for a
person to read.
It is recommended that all subclasses override this method.
The toString
method for class Object
returns a string consisting of the name of the class of which the
object is an instance, the at-sign character `@
', and
the unsigned hexadecimal representation of the hash code of the
object. In other words, this method returns a string equal to the
value of:
getClass().getName() + '@' + Integer.toHexString(hashCode())
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