public class LongAccumulator extends Number implements Serializable
longvalue updated using a supplied function. When updates (method
accumulate(long)) are contended across threads, the set of variables may grow dynamically to reduce contention. Method
longValue()) returns the current value across the variables maintaining updates.
This class is usually preferable to
multiple threads update a common value that is used for purposes such
as collecting statistics, not for fine-grained synchronization
control. Under low update contention, the two classes have similar
characteristics. But under high contention, expected throughput of
this class is significantly higher, at the expense of higher space
The order of accumulation within or across threads is not
guaranteed and cannot be depended upon, so this class is only
applicable to functions for which the order of accumulation does
not matter. The supplied accumulator function should be
side-effect-free, since it may be re-applied when attempted updates
fail due to contention among threads. The function is applied with
the current value as its first argument, and the given update as
the second argument. For example, to maintain a running maximum
value, you could supply
Long::max along with
Long.MIN_VALUE as the identity.
LongAdder provides analogs of the functionality of
this class for the common special case of maintaining counts and
sums. The call
new LongAdder() is equivalent to
LongAccumulator((x, y) -> x + y, 0L.
This class extends
Number, but does not define
methods such as
compareTo because instances are expected to be mutated, and so are
not useful as collection keys.
|Constructor and Description|
Creates a new instance using the given accumulator function and identity element.
|Modifier and Type||Method and Description|
Updates with the given value.
Returns the current value as a
Returns the current value as a
Returns the current value.
Returns the current value as an
Resets variables maintaining updates to the identity value.
Returns the String representation of the current value.
public LongAccumulator(LongBinaryOperator accumulatorFunction, long identity)
accumulatorFunction- a side-effect-free function of two arguments
identity- identity (initial value) for the accumulator function
public void accumulate(long x)
x- the value
public long get()
public void reset()
public long getThenReset()
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.
public String toString()
public long longValue()
public int intValue()
intafter a narrowing primitive conversion.
public float floatValue()
floatafter a widening primitive conversion.
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, 2018, Oracle and/or its affiliates. All rights reserved. Use is subject to license terms. Also see the documentation redistribution policy.