public class DoubleAccumulator extends Number implements Serializable
double
value updated using a supplied function. When updates (method
accumulate(double)
) are contended across threads, the set of variables
may grow dynamically to reduce contention. Method get()
(or, equivalently, doubleValue()
) 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 Double.MINIMUM_VALUE
as the identity. (Class DoubleAdder
provides analogs of the functionality of this class for the common
special case of maintaining 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 |
---|
DoubleAccumulator(DoubleBinaryOperator accumulatorFunction,
double identity)
Creates a new instance using the given accumulator function
and identity element.
|
Modifier and Type | Method and Description |
---|---|
void |
accumulate(double x)
Updates with the given value.
|
double |
doubleValue()
Equivalent to
#sum . |
float |
floatValue()
Returns the
#sum as a float
after a narrowing primitive conversion. |
double |
get()
Returns the current value.
|
double |
getThenReset()
|
int |
intValue()
Returns the
#sum as an int after a
narrowing primitive conversion. |
long |
longValue()
Returns the
#sum as a long after a
narrowing primitive conversion. |
void |
reset()
Resets variables maintaining updates the given value.
|
String |
toString()
Returns the String representation of the
#sum . |
byteValue, shortValue
public DoubleAccumulator(DoubleBinaryOperator accumulatorFunction, double identity)
public void accumulate(double x)
x
- the valuepublic double get()
public void reset()
public double 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()
#sum
.public double doubleValue()
#sum
.doubleValue
in class Number
public long longValue()
#sum
as a long
after a
narrowing primitive conversion.public int intValue()
#sum
as an int
after a
narrowing primitive conversion.public float floatValue()
#sum
as a float
after a narrowing primitive conversion.floatValue
in class Number
float
. 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.
Copyright © 1993, 2013, Oracle and/or its affiliates. All rights reserved.
DRAFT internal-b00