- java.lang.Object
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- java.lang.Number
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- java.util.concurrent.atomic.DoubleAdder
 
 
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- 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
 
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Constructor SummaryConstructors Constructor Description DoubleAdder()Creates a new adder with initial sum of zero.
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Method SummaryAll Methods Instance Methods Concrete Methods Modifier and Type Method 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 declared in class java.lang.NumberbyteValue, shortValue
 
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Method Detail- 
addpublic void add(double x) Adds the given value.- Parameters:
- x- the value to add
 
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sumpublic 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
 
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resetpublic 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.
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sumThenResetpublic 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
 
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doubleValuepublic double doubleValue() Equivalent tosum().- Specified by:
- doubleValuein class- Number
- Returns:
- the sum
 
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longValuepublic long longValue() Returns thesum()as alongafter a narrowing primitive conversion.
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intValuepublic int intValue() Returns thesum()as anintafter a narrowing primitive conversion.
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floatValuepublic float floatValue() Returns thesum()as afloatafter a narrowing primitive conversion.- Specified by:
- floatValuein class- Number
- Returns:
- the numeric value represented by this object after conversion
          to type float.
 
 
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