Class 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

All Methods Instance Methods Concrete Methods Deprecated Methods
Modifier and Type Method Description
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.
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...).
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...).
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...).
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...).
V get()

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

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

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

Returns the current value, with memory semantics of reading as if the variable was declared non-volatile.
void lazySet​(V newValue)

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

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

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

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 Detail

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