jsr166e
Class DoubleAdder
java.lang.Object
java.lang.Number
jsr166e.DoubleAdder
- All Implemented Interfaces:
- Serializable
public class DoubleAdder
- extends Number
- implements Serializable
One or more variables that together maintain an initially zero
double
sum. When updates (method add(double)
) are
contended across threads, the set of variables may grow dynamically
to reduce contention. Method sum()
(or, equivalently doubleValue()
) returns the current total combined across the
variables maintaining the sum.
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
- Since:
- 1.8
- Author:
- Doug Lea
- See Also:
- Serialized Form
Constructor Summary |
DoubleAdder()
Creates a new adder with initial sum of zero. |
Method Summary |
void |
add(double x)
Adds the given value. |
double |
doubleValue()
Equivalent to sum() . |
float |
floatValue()
Returns the sum() as a float
after a narrowing primitive conversion. |
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 the sum to zero. |
double |
sum()
Returns the current sum. |
double |
sumThenReset()
Equivalent in effect to sum() followed by reset() . |
String |
toString()
Returns the String representation of the sum() . |
DoubleAdder
public DoubleAdder()
- Creates a new adder with initial sum of zero.
add
public void add(double x)
- Adds the given value.
- Parameters:
x
- the value to add
sum
public double sum()
- Returns the current sum. The returned value is NOT an
atomic snapshot: Invocation in the absence of concurrent
updates returns an accurate result, but concurrent updates that
occur while the sum is being calculated might not be
incorporated. Also, because double-precision arithmetic is not
strictly associative, the returned result need not be identical
to the value that would be obtained in a sequential series of
updates to a single variable.
- Returns:
- the sum
reset
public void reset()
- Resets variables maintaining the sum to zero. This method may
be a useful alternative to creating a new adder, but is only
effective if there are no concurrent updates. Because this
method is intrinsically racy, it should only be used when it is
known that no threads are concurrently updating.
sumThenReset
public double sumThenReset()
- Equivalent in effect to
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.
- Returns:
- the sum
toString
public String toString()
- Returns the String representation of the
sum()
.
- Overrides:
toString
in class Object
- Returns:
- the String representation of the
sum()
doubleValue
public double doubleValue()
- Equivalent to
sum()
.
- Specified by:
doubleValue
in class Number
- Returns:
- the sum
longValue
public long longValue()
- Returns the
sum()
as a long
after a
narrowing primitive conversion.
- Specified by:
longValue
in class Number
intValue
public int intValue()
- Returns the
sum()
as an int
after a
narrowing primitive conversion.
- Specified by:
intValue
in class Number
floatValue
public float floatValue()
- Returns the
sum()
as a float
after a narrowing primitive conversion.
- Specified by:
floatValue
in class Number
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