Package com.codahale.metrics
Class LongAdder
- java.lang.Object
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- java.lang.Number
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- com.codahale.metrics.Striped64
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- com.codahale.metrics.LongAdder
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- All Implemented Interfaces:
java.io.Serializable
class LongAdder extends Striped64 implements java.io.Serializable
One or more variables that together maintain an initially zerolong
sum. When updates (methodadd(long)
) are contended across threads, the set of variables may grow dynamically to reduce contention. Methodsum()
(or, equivalently,longValue()
) returns the current total combined across the variables maintaining the sum.This class is usually preferable to
AtomicLong
when multiple threads update a common sum 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 consumption.This class extends
Number
, but does not define methods such asequals
,hashCode
andcompareTo
because instances are expected to be mutated, and so are not useful as collection keys.jsr166e note: This class is targeted to be placed in java.util.concurrent.atomic.
- Since:
- 1.8
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Nested Class Summary
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Nested classes/interfaces inherited from class com.codahale.metrics.Striped64
Striped64.Cell, Striped64.HashCode, Striped64.ThreadHashCode
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Field Summary
Fields Modifier and Type Field Description private static long
serialVersionUID
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Constructor Summary
Constructors Constructor Description LongAdder()
Creates a new adder with initial sum of zero.
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Method Summary
All Methods Instance Methods Concrete Methods Modifier and Type Method Description void
add(long x)
Adds the given value.void
decrement()
Equivalent toadd(-1)
.double
doubleValue()
Returns thesum()
as adouble
after a widening primitive conversion.float
floatValue()
Returns thesum()
as afloat
after a widening primitive conversion.(package private) long
fn(long v, long x)
Version of plus for use in retryUpdatevoid
increment()
Equivalent toadd(1)
.int
intValue()
Returns thesum()
as anint
after a narrowing primitive conversion.long
longValue()
Equivalent tosum()
.private void
readObject(java.io.ObjectInputStream s)
void
reset()
Resets variables maintaining the sum to zero.long
sum()
Returns the current sum.long
sumThenReset()
java.lang.String
toString()
Returns the String representation of thesum()
.private void
writeObject(java.io.ObjectOutputStream s)
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Methods inherited from class com.codahale.metrics.Striped64
casBase, casBusy, internalReset, retryUpdate
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Field Detail
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serialVersionUID
private static final long serialVersionUID
- See Also:
- Constant Field Values
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Method Detail
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fn
final long fn(long v, long x)
Version of plus for use in retryUpdate
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add
public void add(long x)
Adds the given value.- Parameters:
x
- the value to add
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increment
public void increment()
Equivalent toadd(1)
.
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decrement
public void decrement()
Equivalent toadd(-1)
.
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sum
public long 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.- Returns:
- the sum
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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.
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sumThenReset
public long 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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toString
public java.lang.String toString()
Returns the String representation of thesum()
.- Overrides:
toString
in classjava.lang.Object
- Returns:
- the String representation of the
sum()
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longValue
public long longValue()
Equivalent tosum()
.- Specified by:
longValue
in classjava.lang.Number
- Returns:
- the sum
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intValue
public int intValue()
Returns thesum()
as anint
after a narrowing primitive conversion.- Specified by:
intValue
in classjava.lang.Number
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floatValue
public float floatValue()
Returns thesum()
as afloat
after a widening primitive conversion.- Specified by:
floatValue
in classjava.lang.Number
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doubleValue
public double doubleValue()
Returns thesum()
as adouble
after a widening primitive conversion.- Specified by:
doubleValue
in classjava.lang.Number
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writeObject
private void writeObject(java.io.ObjectOutputStream s) throws java.io.IOException
- Throws:
java.io.IOException
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readObject
private void readObject(java.io.ObjectInputStream s) throws java.io.IOException, java.lang.ClassNotFoundException
- Throws:
java.io.IOException
java.lang.ClassNotFoundException
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