public class LongAdder extends Number implements Serializable
long
sum. When updates (method add(long)
) are contended
across threads, the set of variables may grow dynamically to reduce
contention. Method sum()
(or, equivalently, longValue()
) returns the current total combined across the
variables maintaining the sum.
This class is usually preferable to AtomicLong
when
multiple threads update a common sum that is used for purposes such
as collecting statistics, not for fine-grained synchronization
control. Under low update contention, the two classes have similar
characteristics. But under high contention, expected throughput of
this class is significantly higher, at the expense of higher space
consumption.
This class extends Number
, but does not define
methods such as hashCode
and compareTo
because
instances are expected to be mutated, and so are not useful as
collection keys.
jsr166e note: This class is targeted to be placed in java.util.concurrent.atomic
Constructor and Description |
---|
LongAdder()
Creates a new adder with initial sum of zero.
|
Modifier and Type | Method and Description |
---|---|
void |
add(long x)
Adds the given value.
|
void |
decrement()
Equivalent to
add(-1) . |
double |
doubleValue()
Returns the
sum() as a double after a widening
primitive conversion. |
float |
floatValue()
Returns the
sum() as a float
after a widening primitive conversion. |
void |
increment()
Equivalent to
add(1) . |
int |
intValue()
Returns the
sum() as an int after a narrowing
primitive conversion. |
long |
longValue()
Equivalent to
sum() . |
void |
reset()
Resets variables maintaining the sum to zero.
|
long |
sum()
Returns the current sum.
|
long |
sumThenReset()
|
String |
toString()
Returns the String representation of the
sum() . |
byteValue, shortValue
public void add(long x)
x
- the value to addpublic void increment()
add(1)
.public void decrement()
add(-1)
.public long sum()
public void reset()
public long sumThenReset()
sum()
followed by reset()
. This method may apply for example during quiescent
points between multithreaded computations. If there are
updates concurrent with this method, the returned value is
not guaranteed to be the final value occurring before
the reset.public long longValue()
sum()
.public int intValue()
sum()
as an int
after a narrowing
primitive conversion.public float floatValue()
sum()
as a float
after a widening primitive conversion.floatValue
in class Number
public double doubleValue()
sum()
as a double
after a widening
primitive conversion.doubleValue
in class Number
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