Added in API level 24

DoubleAdder

open class DoubleAdder : Number, Serializable
kotlin.Any
   ↳ kotlin.Number
   ↳ java.util.concurrent.atomic.DoubleAdder

One or more variables that together maintain an initially zero double sum. When updates (method add) 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. 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 as equals, hashCode and compareTo because instances are expected to be mutated, and so are not useful as collection keys.

Summary

Public constructors

Creates a new adder with initial sum of zero.

Public methods
open Unit
add(x: Double)

Adds the given value.

open Unit

Resets variables maintaining the sum to zero.

open Double
sum()

Returns the current sum.

open Double

Equivalent in effect to sum followed by reset.

open Double

Equivalent to sum.

open Float

Returns the sum as a float after a narrowing primitive conversion.

open Int

Returns the sum as an int after a narrowing primitive conversion.

open Long

Returns the sum as a long after a narrowing primitive conversion.

open String

Returns the String representation of the sum.

Public constructors

DoubleAdder

Added in API level 24
DoubleAdder()

Creates a new adder with initial sum of zero.

Public methods

add

Added in API level 24
open fun add(x: Double): Unit

Adds the given value.

Parameters
x Double: the value to add

reset

Added in API level 24
open fun reset(): Unit

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.

sum

Added in API level 24
open fun sum(): Double

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.

Return
Double the sum

sumThenReset

Added in API level 24
open fun sumThenReset(): Double

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.

Return
Double the sum

toDouble

Added in API level 24
open fun toDouble(): Double

Equivalent to sum.

Return
Double the sum

toFloat

Added in API level 24
open fun toFloat(): Float

Returns the sum as a float after a narrowing primitive conversion.

Return
Float the numeric value represented by this object after conversion to type float.

toInt

Added in API level 24
open fun toInt(): Int

Returns the sum as an int after a narrowing primitive conversion.

Return
Int the numeric value represented by this object after conversion to type int.

toLong

Added in API level 24
open fun toLong(): Long

Returns the sum as a long after a narrowing primitive conversion.

Return
Long the numeric value represented by this object after conversion to type long.

toString

Added in API level 24
open fun toString(): String

Returns the String representation of the sum.

Return
String the String representation of the sum