Module java.base

Package java.util.concurrent.atomic

Class AtomicLongFieldUpdater<T>

java.lang.Object

java.util.concurrent.atomic.AtomicLongFieldUpdater<T>

Type Parameters:

T - The type of the object holding the updatable field

public abstract class AtomicLongFieldUpdater<T>
extends Object

A reflection-based utility that enables atomic updates to designated volatile long fields of designated classes. This class is designed for use in atomic data structures in which several fields of the same node are independently subject to atomic updates.

Note that the guarantees of the compareAndSet method in this class are weaker than in other atomic classes. Because this class cannot ensure that all uses of the field are appropriate for purposes of atomic access, it can guarantee atomicity only with respect to other invocations of compareAndSet and set on the same updater.

Object arguments for parameters of type T that are not instances of the class passed to newUpdater(java.lang.Class<U>, java.lang.String) will result in a ClassCastException being thrown.

Since:

1.5

Constructor Summary

Constructors

Modifier	Constructor	Description
protected	AtomicLongFieldUpdater()	Protected do-nothing constructor for use by subclasses.

Method Summary

Modifier and Type	Method	Description
long	accumulateAndGet(T obj, long x, LongBinaryOperator accumulatorFunction)	Atomically updates (with memory effects as specified by VarHandle.compareAndSet(java.lang.Object...)) the field of the given object managed by this updater with the results of applying the given function to the current and given values, returning the updated value.
long	addAndGet(T obj, long delta)	Atomically adds the given value to the current value of the field of the given object managed by this updater.
abstract boolean	compareAndSet(T obj, long expect, long update)	Atomically sets the field of the given object managed by this updater to the given updated value if the current value == the expected value.
long	decrementAndGet(T obj)	Atomically decrements by one the current value of the field of the given object managed by this updater.
abstract long	get(T obj)	Returns the current value held in the field of the given object managed by this updater.
long	getAndAccumulate(T obj, long x, LongBinaryOperator accumulatorFunction)	Atomically updates (with memory effects as specified by VarHandle.compareAndSet(java.lang.Object...)) the field of the given object managed by this updater with the results of applying the given function to the current and given values, returning the previous value.
long	getAndAdd(T obj, long delta)	Atomically adds the given value to the current value of the field of the given object managed by this updater.
long	getAndDecrement(T obj)	Atomically decrements by one the current value of the field of the given object managed by this updater.
long	getAndIncrement(T obj)	Atomically increments by one the current value of the field of the given object managed by this updater.
long	getAndSet(T obj, long newValue)	Atomically sets the field of the given object managed by this updater to the given value and returns the old value.
long	getAndUpdate(T obj, LongUnaryOperator updateFunction)	Atomically updates (with memory effects as specified by VarHandle.compareAndSet(java.lang.Object...)) the field of the given object managed by this updater with the results of applying the given function, returning the previous value.
long	incrementAndGet(T obj)	Atomically increments by one the current value of the field of the given object managed by this updater.
abstract void	lazySet(T obj, long newValue)	Eventually sets the field of the given object managed by this updater to the given updated value.
static <U> AtomicLongFieldUpdater<U>	newUpdater(Class<U> tclass, String fieldName)	Creates and returns an updater for objects with the given field.
abstract void	set(T obj, long newValue)	Sets the field of the given object managed by this updater to the given updated value.
long	updateAndGet(T obj, LongUnaryOperator updateFunction)	Atomically updates (with memory effects as specified by VarHandle.compareAndSet(java.lang.Object...)) the field of the given object managed by this updater with the results of applying the given function, returning the updated value.
abstract boolean	weakCompareAndSet(T obj, long expect, long update)	Atomically sets the field of the given object managed by this updater to the given updated value if the current value == the expected value.

Methods declared in class java.lang.Object

clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

Constructor Detail

AtomicLongFieldUpdater

protected AtomicLongFieldUpdater()

Protected do-nothing constructor for use by subclasses.

Method Detail

newUpdater

public static <U> AtomicLongFieldUpdater<U> newUpdater(Class<U> tclass,
                                                       String fieldName)

Creates and returns an updater for objects with the given field. The Class argument is needed to check that reflective types and generic types match.

Type Parameters:

U - the type of instances of tclass

Parameters:

tclass - the class of the objects holding the field

fieldName - the name of the field to be updated

Returns:

the updater

Throws:

IllegalArgumentException - if the field is not a volatile long type

RuntimeException - with a nested reflection-based exception if the class does not hold field or is the wrong type, or the field is inaccessible to the caller according to Java language access control

compareAndSet

public abstract boolean compareAndSet(T obj,
                                      long expect,
                                      long update)

Atomically sets the field of the given object managed by this updater to the given updated value if the current value == the expected value. This method is guaranteed to be atomic with respect to other calls to compareAndSet and set, but not necessarily with respect to other changes in the field.

Parameters:

obj - An object whose field to conditionally set

expect - the expected value

update - the new value

Returns:

true if successful

weakCompareAndSet

public abstract boolean weakCompareAndSet(T obj,
                                          long expect,
                                          long update)

Atomically sets the field of the given object managed by this updater to the given updated value if the current value == the expected value. This method is guaranteed to be atomic with respect to other calls to compareAndSet and set, but not necessarily with respect to other changes in the field.

This operation may fail spuriously and does not provide ordering guarantees, so is only rarely an appropriate alternative to compareAndSet.

Parameters:

obj - An object whose field to conditionally set

expect - the expected value

update - the new value

Returns:

true if successful

set

public abstract void set(T obj,
                         long newValue)

Sets the field of the given object managed by this updater to the given updated value. This operation is guaranteed to act as a volatile store with respect to subsequent invocations of compareAndSet.

Parameters:

obj - An object whose field to set

newValue - the new value

lazySet

public abstract void lazySet(T obj,
                             long newValue)

Eventually sets the field of the given object managed by this updater to the given updated value.

Parameters:

obj - An object whose field to set

newValue - the new value

Since:

1.6

get

public abstract long get(T obj)

Returns the current value held in the field of the given object managed by this updater.

Parameters:

obj - An object whose field to get

Returns:

the current value

getAndSet

public long getAndSet(T obj,
                      long newValue)

Atomically sets the field of the given object managed by this updater to the given value and returns the old value.

Parameters:

obj - An object whose field to get and set

newValue - the new value

Returns:

the previous value

getAndIncrement

public long getAndIncrement(T obj)

Atomically increments by one the current value of the field of the given object managed by this updater.

Parameters:

obj - An object whose field to get and set

Returns:

the previous value

getAndDecrement

public long getAndDecrement(T obj)

Atomically decrements by one the current value of the field of the given object managed by this updater.

Parameters:

obj - An object whose field to get and set

Returns:

the previous value

getAndAdd

public long getAndAdd(T obj,
                      long delta)

Atomically adds the given value to the current value of the field of the given object managed by this updater.

Parameters:

obj - An object whose field to get and set

delta - the value to add

Returns:

the previous value

incrementAndGet

public long incrementAndGet(T obj)

Atomically increments by one the current value of the field of the given object managed by this updater.

Parameters:

obj - An object whose field to get and set

Returns:

the updated value

decrementAndGet

public long decrementAndGet(T obj)

Atomically decrements by one the current value of the field of the given object managed by this updater.

Parameters:

obj - An object whose field to get and set

Returns:

the updated value

addAndGet

public long addAndGet(T obj,
                      long delta)

Atomically adds the given value to the current value of the field of the given object managed by this updater.

Parameters:

obj - An object whose field to get and set

delta - the value to add

Returns:

the updated value

getAndUpdate

public final long getAndUpdate(T obj,
                               LongUnaryOperator updateFunction)

Atomically updates (with memory effects as specified by VarHandle.compareAndSet(java.lang.Object...)) the field of the given object managed by this updater with the results of applying the given function, returning the previous value. The function should be side-effect-free, since it may be re-applied when attempted updates fail due to contention among threads.

Parameters:

obj - An object whose field to get and set

updateFunction - a side-effect-free function

Returns:

the previous value

Since:

1.8

updateAndGet

public final long updateAndGet(T obj,
                               LongUnaryOperator updateFunction)

Atomically updates (with memory effects as specified by VarHandle.compareAndSet(java.lang.Object...)) the field of the given object managed by this updater with the results of applying the given function, returning the updated value. The function should be side-effect-free, since it may be re-applied when attempted updates fail due to contention among threads.

Parameters:

obj - An object whose field to get and set

updateFunction - a side-effect-free function

Returns:

the updated value

Since:

1.8

getAndAccumulate

public final long getAndAccumulate(T obj,
                                   long x,
                                   LongBinaryOperator accumulatorFunction)

Atomically updates (with memory effects as specified by VarHandle.compareAndSet(java.lang.Object...)) the field of the given object managed by this updater with the results of applying the given function to the current and given values, returning the previous value. The 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.

Parameters:

obj - An object whose field to get and set

x - the update value

accumulatorFunction - a side-effect-free function of two arguments

Returns:

the previous value

Since:

1.8

accumulateAndGet

public final long accumulateAndGet(T obj,
                                   long x,
                                   LongBinaryOperator accumulatorFunction)

Atomically updates (with memory effects as specified by VarHandle.compareAndSet(java.lang.Object...)) the field of the given object managed by this updater with the results of applying the given function to the current and given values, returning the updated value. The 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.

Parameters:

obj - An object whose field to get and set

x - the update value

accumulatorFunction - a side-effect-free function of two arguments

Returns:

the updated value

Since:

1.8