Module java.base

Package java.util.concurrent.atomic

Class AtomicReference<V>

java.lang.Object

java.util.concurrent.atomic.AtomicReference<V>

Type Parameters:

V - The type of object referred to by this reference

All Implemented Interfaces:

Serializable

public class AtomicReference<V>
extends Object
implements Serializable

An object reference that may be updated atomically. See the VarHandle specification for descriptions of the properties of atomic accesses.

Since:

1.5

See Also:

• Serialized Form

Constructor Summary

Constructors

Constructor	Description
AtomicReference()	Creates a new AtomicReference with null initial value.
AtomicReference(V initialValue)	Creates a new AtomicReference with the given initial value.

Method Summary

Modifier and Type	Method	Description
final V	accumulateAndGet(V x, BinaryOperator<V> accumulatorFunction)	Atomically updates (with memory effects as specified by VarHandle.compareAndSet(java.lang.Object...)) the current value with the results of applying the given function to the current and given values, returning the updated value.
final V	compareAndExchange(V expectedValue, V newValue)	Atomically sets the value to newValue if the current value, referred to as the witness value, == expectedValue, with memory effects as specified by VarHandle.compareAndExchange(java.lang.Object...).
final V	compareAndExchangeAcquire(V expectedValue, V newValue)	Atomically sets the value to newValue if the current value, referred to as the witness value, == expectedValue, with memory effects as specified by VarHandle.compareAndExchangeAcquire(java.lang.Object...).
final V	compareAndExchangeRelease(V expectedValue, V newValue)	Atomically sets the value to newValue if the current value, referred to as the witness value, == expectedValue, with memory effects as specified by VarHandle.compareAndExchangeRelease(java.lang.Object...).
final boolean	compareAndSet(V expectedValue, V newValue)	Atomically sets the value to newValue if the current value == expectedValue, with memory effects as specified by VarHandle.compareAndSet(java.lang.Object...).
final V	get()	Returns the current value, with memory effects as specified by VarHandle.getVolatile(java.lang.Object...).
final V	getAcquire()	Returns the current value, with memory effects as specified by VarHandle.getAcquire(java.lang.Object...).
final V	getAndAccumulate(V x, BinaryOperator<V> accumulatorFunction)	Atomically updates (with memory effects as specified by VarHandle.compareAndSet(java.lang.Object...)) the current value with the results of applying the given function to the current and given values, returning the previous value.
final V	getAndSet(V newValue)	Atomically sets the value to newValue and returns the old value, with memory effects as specified by VarHandle.getAndSet(java.lang.Object...).
final V	getAndUpdate(UnaryOperator<V> updateFunction)	Atomically updates (with memory effects as specified by VarHandle.compareAndSet(java.lang.Object...)) the current value with the results of applying the given function, returning the previous value.
final V	getOpaque()	Returns the current value, with memory effects as specified by VarHandle.getOpaque(java.lang.Object...).
final V	getPlain()	Returns the current value, with memory semantics of reading as if the variable was declared non-volatile.
final void	lazySet(V newValue)	Sets the value to newValue, with memory effects as specified by VarHandle.setRelease(java.lang.Object...).
final void	set(V newValue)	Sets the value to newValue, with memory effects as specified by VarHandle.setVolatile(java.lang.Object...).
final void	setOpaque(V newValue)	Sets the value to newValue, with memory effects as specified by VarHandle.setOpaque(java.lang.Object...).
final void	setPlain(V newValue)	Sets the value to newValue, with memory semantics of setting as if the variable was declared non-volatile and non-final.
final void	setRelease(V newValue)	Sets the value to newValue, with memory effects as specified by VarHandle.setRelease(java.lang.Object...).
String	toString()	Returns the String representation of the current value.
final V	updateAndGet(UnaryOperator<V> updateFunction)	Atomically updates (with memory effects as specified by VarHandle.compareAndSet(java.lang.Object...)) the current value with the results of applying the given function, returning the updated value.
final boolean	weakCompareAndSet(V expectedValue, V newValue)	Deprecated. This method has plain memory effects but the method name implies volatile memory effects (see methods such as compareAndExchange(V, V) and compareAndSet(V, V)).
final boolean	weakCompareAndSetAcquire(V expectedValue, V newValue)	Possibly atomically sets the value to newValue if the current value == expectedValue, with memory effects as specified by VarHandle.weakCompareAndSetAcquire(java.lang.Object...).
final boolean	weakCompareAndSetPlain(V expectedValue, V newValue)	Possibly atomically sets the value to newValue if the current value == expectedValue, with memory effects as specified by VarHandle.weakCompareAndSetPlain(java.lang.Object...).
final boolean	weakCompareAndSetRelease(V expectedValue, V newValue)	Possibly atomically sets the value to newValue if the current value == expectedValue, with memory effects as specified by VarHandle.weakCompareAndSetRelease(java.lang.Object...).
final boolean	weakCompareAndSetVolatile(V expectedValue, V newValue)	Possibly atomically sets the value to newValue if the current value == expectedValue, with memory effects as specified by VarHandle.weakCompareAndSet(java.lang.Object...).

Methods declared in class java.lang.Object

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

Constructor Details

AtomicReference

public AtomicReference(V initialValue)

Creates a new AtomicReference with the given initial value.

Parameters:

initialValue - the initial value

AtomicReference

public AtomicReference()

Creates a new AtomicReference with null initial value.

Method Details

get

public final V get()

Returns the current value, with memory effects as specified by VarHandle.getVolatile(java.lang.Object...).

Returns:

the current value

set

public final void set(V newValue)

Sets the value to newValue, with memory effects as specified by VarHandle.setVolatile(java.lang.Object...).

Parameters:

newValue - the new value

lazySet

public final void lazySet(V newValue)

Sets the value to newValue, with memory effects as specified by VarHandle.setRelease(java.lang.Object...).

Parameters:

newValue - the new value

Since:

1.6

compareAndSet

public final boolean compareAndSet(V expectedValue,
 V newValue)

Atomically sets the value to newValue if the current value == expectedValue, with memory effects as specified by VarHandle.compareAndSet(java.lang.Object...).

Parameters:

expectedValue - the expected value

newValue - the new value

Returns:

true if successful. False return indicates that the actual value was not equal to the expected value.

weakCompareAndSet

@Deprecated(since="9")
public final boolean weakCompareAndSet(V expectedValue,
 V newValue)

Deprecated.

This method has plain memory effects but the method name implies volatile memory effects (see methods such as compareAndExchange(V, V) and compareAndSet(V, V)). To avoid confusion over plain or volatile memory effects it is recommended that the method weakCompareAndSetPlain(V, V) be used instead.

Possibly atomically sets the value to newValue if the current value == expectedValue, with memory effects as specified by VarHandle.weakCompareAndSetPlain(java.lang.Object...).

Parameters:

expectedValue - the expected value

newValue - the new value

Returns:

true if successful

See Also:

• weakCompareAndSetPlain(V, V)

weakCompareAndSetPlain

public final boolean weakCompareAndSetPlain(V expectedValue,
 V newValue)

Possibly atomically sets the value to newValue if the current value == expectedValue, with memory effects as specified by VarHandle.weakCompareAndSetPlain(java.lang.Object...).

Parameters:

expectedValue - the expected value

newValue - the new value

Returns:

true if successful

Since:

9

getAndSet

public final V getAndSet(V newValue)

Atomically sets the value to newValue and returns the old value, with memory effects as specified by VarHandle.getAndSet(java.lang.Object...).

Parameters:

newValue - the new value

Returns:

the previous value

getAndUpdate

public final V getAndUpdate(UnaryOperator<V> updateFunction)

Atomically updates (with memory effects as specified by VarHandle.compareAndSet(java.lang.Object...)) the current value 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:

updateFunction - a side-effect-free function

Returns:

the previous value

Since:

1.8

updateAndGet

public final V updateAndGet(UnaryOperator<V> updateFunction)

Atomically updates (with memory effects as specified by VarHandle.compareAndSet(java.lang.Object...)) the current value 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:

updateFunction - a side-effect-free function

Returns:

the updated value

Since:

1.8

getAndAccumulate

public final V getAndAccumulate(V x,
 BinaryOperator<V> accumulatorFunction)

Atomically updates (with memory effects as specified by VarHandle.compareAndSet(java.lang.Object...)) the current value 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:

x - the update value

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

Returns:

the previous value

Since:

1.8

accumulateAndGet

public final V accumulateAndGet(V x,
 BinaryOperator<V> accumulatorFunction)

Atomically updates (with memory effects as specified by VarHandle.compareAndSet(java.lang.Object...)) the current value 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:

x - the update value

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

Returns:

the updated value

Since:

1.8

toString

public String toString()

Returns the String representation of the current value.

Overrides:

toString in class Object

Returns:

the String representation of the current value

getPlain

public final V getPlain()

Returns the current value, with memory semantics of reading as if the variable was declared non-volatile.

Returns:

the value

Since:

9

setPlain

public final void setPlain(V newValue)

Sets the value to newValue, with memory semantics of setting as if the variable was declared non-volatile and non-final.

Parameters:

newValue - the new value

Since:

9

getOpaque

public final V getOpaque()

Returns the current value, with memory effects as specified by VarHandle.getOpaque(java.lang.Object...).

Returns:

the value

Since:

9

setOpaque

public final void setOpaque(V newValue)

Sets the value to newValue, with memory effects as specified by VarHandle.setOpaque(java.lang.Object...).

Parameters:

newValue - the new value

Since:

9

getAcquire

public final V getAcquire()

Returns the current value, with memory effects as specified by VarHandle.getAcquire(java.lang.Object...).

Returns:

the value

Since:

9

setRelease

public final void setRelease(V newValue)

Sets the value to newValue, with memory effects as specified by VarHandle.setRelease(java.lang.Object...).

Parameters:

newValue - the new value

Since:

9

compareAndExchange

public final V compareAndExchange(V expectedValue,
 V newValue)

Atomically sets the value to newValue if the current value, referred to as the witness value, == expectedValue, with memory effects as specified by VarHandle.compareAndExchange(java.lang.Object...).

Parameters:

expectedValue - the expected value

newValue - the new value

Returns:

the witness value, which will be the same as the expected value if successful

Since:

9

compareAndExchangeAcquire

public final V compareAndExchangeAcquire(V expectedValue,
 V newValue)

Atomically sets the value to newValue if the current value, referred to as the witness value, == expectedValue, with memory effects as specified by VarHandle.compareAndExchangeAcquire(java.lang.Object...).

Parameters:

expectedValue - the expected value

newValue - the new value

Returns:

the witness value, which will be the same as the expected value if successful

Since:

9

compareAndExchangeRelease

public final V compareAndExchangeRelease(V expectedValue,
 V newValue)

Atomically sets the value to newValue if the current value, referred to as the witness value, == expectedValue, with memory effects as specified by VarHandle.compareAndExchangeRelease(java.lang.Object...).

Parameters:

expectedValue - the expected value

newValue - the new value

Returns:

the witness value, which will be the same as the expected value if successful

Since:

9

weakCompareAndSetVolatile

public final boolean weakCompareAndSetVolatile(V expectedValue,
 V newValue)

Possibly atomically sets the value to newValue if the current value == expectedValue, with memory effects as specified by VarHandle.weakCompareAndSet(java.lang.Object...).

Parameters:

expectedValue - the expected value

newValue - the new value

Returns:

true if successful

Since:

9

weakCompareAndSetAcquire

public final boolean weakCompareAndSetAcquire(V expectedValue,
 V newValue)

Possibly atomically sets the value to newValue if the current value == expectedValue, with memory effects as specified by VarHandle.weakCompareAndSetAcquire(java.lang.Object...).

Parameters:

expectedValue - the expected value

newValue - the new value

Returns:

true if successful

Since:

9

weakCompareAndSetRelease

public final boolean weakCompareAndSetRelease(V expectedValue,
 V newValue)

Possibly atomically sets the value to newValue if the current value == expectedValue, with memory effects as specified by VarHandle.weakCompareAndSetRelease(java.lang.Object...).

Parameters:

expectedValue - the expected value

newValue - the new value

Returns:

true if successful

Since:

9