AtomicStampedReference (Java Platform SE 6)

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java.util.concurrent.atomic
class AtomicStampedReference

java.lang.Object
  java.util.concurrent.atomic.AtomicStampedReference

Most common way to construct:

Integer one = …;

AtomicStampedReference ai = new AtomicStampedReference(one, 0);

Based on 34 examples

public class AtomicStampedReference
extends Object

An {@code 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.

Constructor Summary
`AtomicStampedReference(Object initialRef, int initialStamp)` Creates a new with the given initial values.

Method Summary
`boolean`	`attemptStamp(Object 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(Object expectedReference, Object 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.
`Object`	`get(int[] stampHolder)` Returns the current values of both the reference and the stamp.
`Object`	`getReference()` Returns the current value of the reference.
`int`	`getStamp()` Returns the current value of the stamp.
`void`	`set(Object newReference, int newStamp)` Unconditionally sets the value of both the reference and stamp.
`boolean`	`weakCompareAndSet(Object expectedReference, Object 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(Object initialRef,
                              int initialStamp)

Creates a new {@code AtomicStampedReference} with the given initial values.

Parameters:: initialRef - the initial reference; initialStamp - the initial stamp

Method Detail

attemptStamp

public boolean attemptStamp(Object expectedReference,
                            int newStamp)

Atomically sets the value of the stamp to the given update value if the current reference is {@code ==} to the expected reference. Any given invocation of this operation may fail (return {@code 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

compareAndSet

public boolean compareAndSet(Object expectedReference,
                             Object 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 {@code ==} 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

get

public Object get(int[] stampHolder)

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

Parameters:: stampHolder - an array of size of at least one. On return, {@code stampholder[0]} will hold the value of the stamp.
Returns:: the current value of the reference

getReference

public Object 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

set

public void set(Object 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

weakCompareAndSet

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

May fail spuriously and does not provide ordering guarantees, so is only rarely an appropriate alternative to {@code 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