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Added in API level 24

Summary: Ctors | Methods | Inherited Methods | [Expand All]

DoubleAdder

public class DoubleAdder
extends Number implements Serializable

java.lang.Object
↳	java.lang.Number
	↳	java.util.concurrent.atomic.DoubleAdder

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. 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
`DoubleAdder()` Creates a new adder with initial sum of zero.

Public methods
`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()`.

Inherited methods

From class


  
    java.lang.Number

From class


  
    java.lang.Object

`Object`	`clone()` Creates and returns a copy of this object.
`boolean`	`equals(Object obj)` Indicates whether some other object is "equal to" this one.
`void`	`finalize()` Called by the garbage collector on an object when garbage collection determines that there are no more references to the object.
`final Class<?>`	`getClass()` Returns the runtime class of this `Object`.
`int`	`hashCode()` Returns a hash code value for the object.
`final void`	`notify()` Wakes up a single thread that is waiting on this object's monitor.
`final void`	`notifyAll()` Wakes up all threads that are waiting on this object's monitor.
`String`	`toString()` Returns a string representation of the object.
`final void`	`wait(long millis, int nanos)` Causes the current thread to wait until another thread invokes the `notify()` method or the `notifyAll()` method for this object, or some other thread interrupts the current thread, or a certain amount of real time has elapsed.
`final void`	`wait(long millis)` Causes the current thread to wait until either another thread invokes the `notify()` method or the `notifyAll()` method for this object, or a specified amount of time has elapsed.
`final void`	`wait()` Causes the current thread to wait until another thread invokes the `notify()` method or the `notifyAll()` method for this object.

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

void add (double x)

Adds the given value.

Parameters
`x`	`double`: the value to add

doubleValue

Added in API level 24

double doubleValue ()

Equivalent to sum().

Returns
`double`	the sum

floatValue

Added in API level 24

float floatValue ()

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

Returns
`float`	the numeric value represented by this object after conversion to type `float`.

intValue

Added in API level 24

int intValue ()

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

Returns
`int`	the numeric value represented by this object after conversion to type `int`.

longValue

Added in API level 24

long longValue ()

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

Returns
`long`	the numeric value represented by this object after conversion to type `long`.

reset

Added in API level 24

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.

sum

Added in API level 24

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
`double`	the sum

sumThenReset

Added in API level 24

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
`double`	the sum

toString

Added in API level 24

String toString ()

Returns the String representation of the sum().

Returns
`String`	the String representation of the `sum()`