java.util.concurrent.atomic
Class AtomicStampedReference<V>

java.lang.Object
  java.util.concurrent.atomic.AtomicStampedReference<V>

Type Parameters:

V - The type of object referred to by this reference

public class AtomicStampedReference<V>
extends Object

An AtomicStampedReference maintains an object reference along with an integer "stamp", that can be updated atomically.

Implementation note. This implementation maintains stamped references by creating internal objects representing "boxed" [reference, integer] pairs.

Since:

1.5

Constructor Summary

AtomicStampedReference(V initialRef, int initialStamp)
Creates a new AtomicStampedReference with the given initial values.

Method Summary

boolean	attemptStamp(V expectedReference, int newStamp) Atomically sets the value of the stamp to the given update value if the current reference is == to the expected reference.
boolean	compareAndSet(V expectedReference, V newReference, int expectedStamp, int newStamp) Atomically sets the value of both the reference and stamp to the given update values if the current reference is == to the expected reference and the current stamp is equal to the expected stamp.
V	get(int[] stampHolder) Returns the current values of both the reference and the stamp.
V	getReference() Returns the current value of the reference.
int	getStamp() Returns the current value of the stamp.
void	set(V newReference, int newStamp) Unconditionally sets the value of both the reference and stamp.
boolean	weakCompareAndSet(V expectedReference, V newReference, int expectedStamp, int newStamp) Atomically sets the value of both the reference and stamp to the given update values if the current reference is == to the expected reference and the current stamp is equal to the expected stamp.

Methods inherited from class java.lang.Object

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

Constructor Detail

AtomicStampedReference

public AtomicStampedReference(V initialRef,
                              int initialStamp)

Creates a new AtomicStampedReference with the given initial values.

Parameters:

initialRef - the initial reference

initialStamp - the initial stamp

Method Detail

getReference

public V getReference()

Returns the current value of the reference.

Returns:

the current value of the reference

getStamp

public int getStamp()

Returns the current value of the stamp.

Returns:

the current value of the stamp

get

public V get(int[] stampHolder)

Returns the current values of both the reference and the stamp. Typical usage is int[1] holder; ref = v.get(holder); .

Parameters:

stampHolder - an array of size of at least one. On return, stampholder[0] will hold the value of the stamp.

Returns:

the current value of the reference

weakCompareAndSet

public boolean weakCompareAndSet(V expectedReference,
                                 V newReference,
                                 int expectedStamp,
                                 int newStamp)

Atomically sets the value of both the reference and stamp to the given update values if the current reference is == to the expected reference and the current stamp is equal to the expected stamp.

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

Parameters:

expectedReference - the expected value of the reference

newReference - the new value for the reference

expectedStamp - the expected value of the stamp

newStamp - the new value for the stamp

Returns:

true if successful

compareAndSet

public boolean compareAndSet(V expectedReference,
                             V newReference,
                             int expectedStamp,
                             int newStamp)

Atomically sets the value of both the reference and stamp to the given update values if the current reference is == to the expected reference and the current stamp is equal to the expected stamp.

Parameters:

expectedReference - the expected value of the reference

newReference - the new value for the reference

expectedStamp - the expected value of the stamp

newStamp - the new value for the stamp

Returns:

true if successful

set

public void set(V newReference,
                int newStamp)

Unconditionally sets the value of both the reference and stamp.

Parameters:

newReference - the new value for the reference

newStamp - the new value for the stamp

attemptStamp

public boolean attemptStamp(V expectedReference,
                            int newStamp)

Atomically sets the value of the stamp to the given update value if the current reference is == to the expected reference. Any given invocation of this operation may fail (return false) spuriously, but repeated invocation when the current value holds the expected value and no other thread is also attempting to set the value will eventually succeed.

Parameters:

expectedReference - the expected value of the reference

newStamp - the new value for the stamp

Returns:

true if successful