public class LongAccumulator extends Number implements Serializable
long
value updated using a supplied function. When updates (method
accumulate(long)
) are contended across threads, the set of variables
may grow dynamically to reduce contention. Method get()
(or, equivalently, longValue()
) returns the current value
across the variables maintaining updates.
The supplied accumulator function must be side-effect-free. It
may be re-applied when attempted updates fail due to contention
among threads. The function is applied with the current value as
its first argument, and the given update as the second argument.
For example, to maintain a running maximum value, you could supply
(x, y) -> (y > x) ? y : x
along with Long.MINIMUM_VALUE
as the identity. (Class LongAdder
provides analogs of the functionality of this class for the common
special case of maintaining counts and sums.)
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.
Constructor and Description |
---|
LongAccumulator(LongBinaryOperator accumulatorFunction,
long identity)
Creates a new instance using the given accumulator function
and identity element.
|
Modifier and Type | Method and Description |
---|---|
void |
accumulate(long x)
Updates with the given value.
|
double |
doubleValue()
Returns the
get() as a double after a widening
primitive conversion. |
float |
floatValue()
Returns the
get() as a float
after a widening primitive conversion. |
long |
get()
Returns the current value.
|
long |
getThenReset()
|
int |
intValue()
Returns the
get() as an int after a narrowing
primitive conversion. |
long |
longValue()
Equivalent to
get() . |
void |
reset()
Resets variables maintaining updates the given value.
|
String |
toString()
Returns the String representation of the current value.
|
byteValue, shortValue
public LongAccumulator(LongBinaryOperator accumulatorFunction, long identity)
public void accumulate(long x)
x
- the valuepublic long get()
public void reset()
public long getThenReset()
get()
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 String toString()
public long longValue()
get()
.public int intValue()
get()
as an int
after a narrowing
primitive conversion.public float floatValue()
get()
as a float
after a widening primitive conversion.floatValue
in class Number
float
.public double doubleValue()
get()
as a double
after a widening
primitive conversion.doubleValue
in class Number
double
. Submit a bug or feature
For further API reference and developer documentation, see Java SE Documentation. That documentation contains more detailed, developer-targeted descriptions, with conceptual overviews, definitions of terms, workarounds, and working code examples.
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