public class LongAdder extends Striped64 implements java.io.Serializable
long
sum. When updates (method add(long)
) are contended
across threads, the set of variables may grow dynamically to reduce
contention. Method sum()
(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 as equals
, hashCode
and compareTo
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.
Striped64.Cell, Striped64.HashCode, Striped64.ThreadHashCode
Modifier and Type | Field and Description |
---|---|
private static long |
serialVersionUID |
Constructor and Description |
---|
LongAdder()
Creates a new adder with initial sum of zero.
|
Modifier and Type | Method and Description |
---|---|
void |
add(long x)
Adds the given value.
|
void |
decrement()
Equivalent to
add(-1) . |
double |
doubleValue()
Returns the
sum() as a double after a widening
primitive conversion. |
float |
floatValue()
Returns the
sum() as a float
after a widening primitive conversion. |
(package private) long |
fn(long v,
long x)
Version of plus for use in retryUpdate
|
void |
increment()
Equivalent to
add(1) . |
int |
intValue()
Returns the
sum() as an int after a narrowing
primitive conversion. |
long |
longValue()
Equivalent to
sum() . |
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 the
sum() . |
private void |
writeObject(java.io.ObjectOutputStream s) |
casBase, casBusy, internalReset, retryUpdate
private static final long serialVersionUID
final long fn(long v, long x)
public void add(long x)
x
- the value to addpublic void increment()
add(1)
.public void decrement()
add(-1)
.public long sum()
public void reset()
public long sumThenReset()
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.public java.lang.String toString()
sum()
.toString
in class java.lang.Object
sum()
public long longValue()
sum()
.longValue
in class java.lang.Number
public int intValue()
sum()
as an int
after a narrowing
primitive conversion.intValue
in class java.lang.Number
public float floatValue()
sum()
as a float
after a widening primitive conversion.floatValue
in class java.lang.Number
public double doubleValue()
sum()
as a double
after a widening
primitive conversion.doubleValue
in class java.lang.Number
private void writeObject(java.io.ObjectOutputStream s) throws java.io.IOException
java.io.IOException
private void readObject(java.io.ObjectInputStream s) throws java.io.IOException, java.lang.ClassNotFoundException
java.io.IOException
java.lang.ClassNotFoundException