Module java.base

Package java.util.concurrent.atomic

Class AtomicReferenceArray<E>

java.lang.Object

java.util.concurrent.atomic.AtomicReferenceArray<E>

Type Parameters:

E - The base class of elements held in this array

All Implemented Interfaces:

Serializable

public class AtomicReferenceArray<E>
extends Object
implements Serializable

An array of object references in which elements 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
AtomicReferenceArray(int length)	Creates a new AtomicReferenceArray of the given length, with all elements initially null.
AtomicReferenceArray(E[] array)	Creates a new AtomicReferenceArray with the same length as, and all elements copied from, the given array.

Method Summary

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

AtomicReferenceArray

public AtomicReferenceArray(int length)

Creates a new AtomicReferenceArray of the given length, with all elements initially null.

Parameters:

length - the length of the array

AtomicReferenceArray

public AtomicReferenceArray(E[] array)

Creates a new AtomicReferenceArray with the same length as, and all elements copied from, the given array.

Parameters:

array - the array to copy elements from

Throws:

NullPointerException - if array is null

Method Details

length

public final int length()

Returns the length of the array.

Returns:

the length of the array

get

public final E get(int i)

Returns the current value of the element at index i, with memory effects as specified by VarHandle.getVolatile(java.lang.Object...).

Parameters:

i - the index

Returns:

the current value

set

public final void set(int i,
 E newValue)

Sets the element at index i to newValue, with memory effects as specified by VarHandle.setVolatile(java.lang.Object...).

Parameters:

i - the index

newValue - the new value

lazySet

public final void lazySet(int i,
 E newValue)

Sets the element at index i to newValue, with memory effects as specified by VarHandle.setRelease(java.lang.Object...).

Parameters:

i - the index

newValue - the new value

Since:

1.6

getAndSet

public final E getAndSet(int i,
 E newValue)

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

Parameters:

i - the index

newValue - the new value

Returns:

the previous value

compareAndSet

public final boolean compareAndSet(int i,
 E expectedValue,
 E newValue)

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

Parameters:

i - the index

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(int i,
 E expectedValue,
 E newValue)

Deprecated.

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

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

Parameters:

i - the index

expectedValue - the expected value

newValue - the new value

Returns:

true if successful

See Also:

• weakCompareAndSetPlain(int, E, E)

weakCompareAndSetPlain

public final boolean weakCompareAndSetPlain(int i,
 E expectedValue,
 E newValue)

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

Parameters:

i - the index

expectedValue - the expected value

newValue - the new value

Returns:

true if successful

Since:

9

getAndUpdate

public final E getAndUpdate(int i,
 UnaryOperator<E> updateFunction)

Atomically updates (with memory effects as specified by VarHandle.compareAndSet(java.lang.Object...)) the element at index i 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:

i - the index

updateFunction - a side-effect-free function

Returns:

the previous value

Since:

1.8

updateAndGet

public final E updateAndGet(int i,
 UnaryOperator<E> updateFunction)

Atomically updates (with memory effects as specified by VarHandle.compareAndSet(java.lang.Object...)) the element at index i 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:

i - the index

updateFunction - a side-effect-free function

Returns:

the updated value

Since:

1.8

getAndAccumulate

public final E getAndAccumulate(int i,
 E x,
 BinaryOperator<E> accumulatorFunction)

Atomically updates (with memory effects as specified by VarHandle.compareAndSet(java.lang.Object...)) the element at index i 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 of the element at index i as its first argument, and the given update as the second argument.

Parameters:

i - the index

x - the update value

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

Returns:

the previous value

Since:

1.8

accumulateAndGet

public final E accumulateAndGet(int i,
 E x,
 BinaryOperator<E> accumulatorFunction)

Atomically updates (with memory effects as specified by VarHandle.compareAndSet(java.lang.Object...)) the element at index i 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 of the element at index i as its first argument, and the given update as the second argument.

Parameters:

i - the index

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 values of array.

Overrides:

toString in class Object

Returns:

the String representation of the current values of array

getPlain

public final E getPlain(int i)

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

Parameters:

i - the index

Returns:

the value

Since:

9

setPlain

public final void setPlain(int i,
 E newValue)

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

Parameters:

i - the index

newValue - the new value

Since:

9

getOpaque

public final E getOpaque(int i)

Returns the current value of the element at index i, with memory effects as specified by VarHandle.getOpaque(java.lang.Object...).

Parameters:

i - the index

Returns:

the value

Since:

9

setOpaque

public final void setOpaque(int i,
 E newValue)

Sets the element at index i to newValue, with memory effects as specified by VarHandle.setOpaque(java.lang.Object...).

Parameters:

i - the index

newValue - the new value

Since:

9

getAcquire

public final E getAcquire(int i)

Returns the current value of the element at index i, with memory effects as specified by VarHandle.getAcquire(java.lang.Object...).

Parameters:

i - the index

Returns:

the value

Since:

9

setRelease

public final void setRelease(int i,
 E newValue)

Sets the element at index i to newValue, with memory effects as specified by VarHandle.setRelease(java.lang.Object...).

Parameters:

i - the index

newValue - the new value

Since:

9

compareAndExchange

public final E compareAndExchange(int i,
 E expectedValue,
 E newValue)

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

Parameters:

i - the index

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 E compareAndExchangeAcquire(int i,
 E expectedValue,
 E newValue)

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

Parameters:

i - the index

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 E compareAndExchangeRelease(int i,
 E expectedValue,
 E newValue)

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

Parameters:

i - the index

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(int i,
 E expectedValue,
 E newValue)

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

Parameters:

i - the index

expectedValue - the expected value

newValue - the new value

Returns:

true if successful

Since:

9

weakCompareAndSetAcquire

public final boolean weakCompareAndSetAcquire(int i,
 E expectedValue,
 E newValue)

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

Parameters:

i - the index

expectedValue - the expected value

newValue - the new value

Returns:

true if successful

Since:

9

weakCompareAndSetRelease

public final boolean weakCompareAndSetRelease(int i,
 E expectedValue,
 E newValue)

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

Parameters:

i - the index

expectedValue - the expected value

newValue - the new value

Returns:

true if successful

Since:

9