AtomicReference

AI-generated Key Takeaways

• AtomicReference provides a way to update object references atomically, ensuring thread safety.

• It offers methods for setting, getting, and comparing values, along with atomic update operations using functions.

• Constructors allow initialization with a given value or with null.

• weakCompareAndSet may spuriously fail and is rarely a suitable replacement for compareAndSet.

• AtomicReference is part of the java.util.concurrent.atomic package for thread-safe programming.

public class AtomicReference extends Object
implements Serializable

An object reference that may be updated atomically. See the java.util.concurrent.atomic package specification for description of the properties of atomic variables.

Public Constructor Summary

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

Public Method Summary

final V	accumulateAndGet(V x, BinaryOperator<V> accumulatorFunction) Atomically updates the current value with the results of applying the given function to the current and given values, returning the updated value.
final boolean	compareAndSet(V expect, V update) Atomically sets the value to the given updated value if the current value == the expected value.
final V	get() Gets the current value.
final V	getAndAccumulate(V x, BinaryOperator<V> accumulatorFunction) Atomically updates 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 to the given value and returns the old value.
final V	getAndUpdate(UnaryOperator<V> updateFunction) Atomically updates the current value with the results of applying the given function, returning the previous value.
final void	lazySet(V newValue) Eventually sets to the given value.
final void	set(V newValue) Sets to the given value.
String	toString() Returns the String representation of the current value.
final V	updateAndGet(UnaryOperator<V> updateFunction) Atomically updates the current value with the results of applying the given function, returning the updated value.
final boolean	weakCompareAndSet(V expect, V update) Atomically sets the value to the given updated value if the current value == the expected value.

Inherited Method Summary

From class java.lang.Object

Object	clone() Creates and returns a copy of this Object.
boolean	equals(Object obj) Compares this instance with the specified object and indicates if they are equal.
void	finalize() Invoked when the garbage collector has detected that this instance is no longer reachable.
final Class<?>	getClass() Returns the unique instance of Class that represents this object's class.
int	hashCode() Returns an integer hash code for this object.
final void	notify() Causes a thread which is waiting on this object's monitor (by means of calling one of the wait() methods) to be woken up.
final void	notifyAll() Causes all threads which are waiting on this object's monitor (by means of calling one of the wait() methods) to be woken up.
String	toString() Returns a string containing a concise, human-readable description of this object.
final void	wait(long timeout, int nanos) Causes the calling thread to wait until another thread calls the notify() or notifyAll() method of this object or until the specified timeout expires.
final void	wait(long timeout) Causes the calling thread to wait until another thread calls the notify() or notifyAll() method of this object or until the specified timeout expires.
final void	wait() Causes the calling thread to wait until another thread calls the notify() or notifyAll() method of this object.

Public Constructors

public AtomicReference (V initialValue)

Creates a new AtomicReference with the given initial value.

Parameters

initialValue	the initial value

public AtomicReference ()

Creates a new AtomicReference with null initial value.

Public Methods

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

Atomically updates 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

public final boolean compareAndSet (V expect, V update)

Atomically sets the value to the given updated value if the current value == the expected value.

Parameters

expect	the expected value
update	the new value

Returns

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

public final V get ()

Gets the current value.

Returns

• the current value

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

Atomically updates 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

public final V getAndSet (V newValue)

Atomically sets to the given value and returns the old value.

Parameters

newValue	the new value

Returns

• the previous value

public final V getAndUpdate (UnaryOperator<V> updateFunction)

Atomically updates 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

public final void lazySet (V newValue)

Eventually sets to the given value.

Parameters

newValue	the new value

public final void set (V newValue)

Sets to the given value.

Parameters

newValue	the new value

public String toString ()

Returns the String representation of the current value.

Returns

• the String representation of the current value

public final V updateAndGet (UnaryOperator<V> updateFunction)

Atomically updates 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

public final boolean weakCompareAndSet (V expect, V update)

Atomically sets the value to the given updated value if the current value == the expected value.

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

Parameters

expect	the expected value
update	the new value

Returns

• true if successful