compact1, compact2, compact3
java.util.concurrent.atomic
Class DoubleAdder
- java.lang.Object
-
- java.lang.Number
-
- java.util.concurrent.atomic.DoubleAdder
-
- All Implemented Interfaces:
- Serializable
public class DoubleAdder extends Number implements Serializable
One or more variables that together maintain an initially zerodoublesum. When updates (methodadd(double)) are contended across threads, the set of variables may grow dynamically to reduce contention. Methodsum()(or, equivalentlydoubleValue()) returns the current total combined across the variables maintaining the sum. The order of accumulation within or across threads is not guaranteed. Thus, this class may not be applicable if numerical stability is required, especially when combining values of substantially different orders of magnitude.This class is usually preferable to alternatives when multiple threads update a common value that is used for purposes such as summary statistics that are frequently updated but less frequently read.
This class extends
Number, but does not define methods such asequals,hashCodeandcompareTobecause instances are expected to be mutated, and so are not useful as collection keys.- Since:
- 1.8
- See Also:
- Serialized Form
-
-
Constructor Summary
Constructors Constructor and Description DoubleAdder()Creates a new adder with initial sum of zero.
-
Method Summary
All Methods Instance Methods Concrete Methods Modifier and Type Method and Description voidadd(double x)Adds the given value.doubledoubleValue()Equivalent tosum().floatfloatValue()Returns thesum()as afloatafter a narrowing primitive conversion.intintValue()Returns thesum()as anintafter a narrowing primitive conversion.longlongValue()Returns thesum()as alongafter a narrowing primitive conversion.voidreset()Resets variables maintaining the sum to zero.doublesum()Returns the current sum.doublesumThenReset()StringtoString()Returns the String representation of thesum().-
Methods inherited from class java.lang.Number
byteValue, shortValue
-
-
-
-
Method Detail
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 floating-point 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 tosum()followed byreset(). 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
doubleValue
public double doubleValue()
Equivalent tosum().- Specified by:
-
doubleValuein classNumber - Returns:
- the sum
longValue
public long longValue()
Returns thesum()as alongafter a narrowing primitive conversion.
intValue
public int intValue()
Returns thesum()as anintafter a narrowing primitive conversion.
floatValue
public float floatValue()
Returns thesum()as afloatafter a narrowing primitive conversion.- Specified by:
-
floatValuein classNumber - Returns:
-
the numeric value represented by this object after conversion to type
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, 2022, Oracle and/or its affiliates. All rights reserved. Use is subject to license terms. Also see the documentation redistribution policy.
