AtomicMarkableReference (Java Platform SE 6)

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java.util.concurrent.atomic
class AtomicMarkableReference

java.lang.Object
  java.util.concurrent.atomic.AtomicMarkableReference

Most common way to construct:

Integer one = …;

AtomicMarkableReference ai = new AtomicMarkableReference(one, false);

Based on 17 examples

public class AtomicMarkableReference
extends Object

An {@code AtomicMarkableReference} maintains an object reference along with a mark bit, that can be updated atomically.

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

Constructor Summary
`AtomicMarkableReference(Object initialRef, boolean initialMark)` Creates a new with the given initial values.

Method Summary
`boolean`	`attemptMark(Object expectedReference, boolean newMark)` Atomically sets the value of the mark to the given update value if the current reference is to the expected reference.
`boolean`	`compareAndSet(Object expectedReference, Object newReference, boolean expectedMark, boolean newMark)` Atomically sets the value of both the reference and mark to the given update values if the current reference is to the expected reference and the current mark is equal to the expected mark.
`Object`	`get(boolean[] markHolder)` Returns the current values of both the reference and the mark.
`Object`	`getReference()` Returns the current value of the reference.
`boolean`	`isMarked()` Returns the current value of the mark.
`void`	`set(Object newReference, boolean newMark)` Unconditionally sets the value of both the reference and mark.
`boolean`	`weakCompareAndSet(Object expectedReference, Object newReference, boolean expectedMark, boolean newMark)` Atomically sets the value of both the reference and mark to the given update values if the current reference is to the expected reference and the current mark is equal to the expected mark.

Methods inherited from class java.lang.Object
`clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait`

Constructor Detail

AtomicMarkableReference

public AtomicMarkableReference(Object initialRef,
                               boolean initialMark)

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

Parameters:: initialRef - the initial reference; initialMark - the initial mark

Method Detail

attemptMark

public boolean attemptMark(Object expectedReference,
                           boolean newMark)

Atomically sets the value of the mark 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; newMark - the new value for the mark
Returns:: true if successful

compareAndSet

public boolean compareAndSet(Object expectedReference,
                             Object newReference,
                             boolean expectedMark,
                             boolean newMark)

Atomically sets the value of both the reference and mark to the given update values if the current reference is {@code ==} to the expected reference and the current mark is equal to the expected mark.

Parameters:: expectedReference - the expected value of the reference; newReference - the new value for the reference; expectedMark - the expected value of the mark; newMark - the new value for the mark
Returns:: true if successful

get

public Object get(boolean[] markHolder)

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

Parameters:: markHolder - an array of size of at least one. On return, {@code markholder[0]} will hold the value of the mark.
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

isMarked

public boolean isMarked()

Returns the current value of the mark.

Returns:: the current value of the mark

set

public void set(Object newReference,
                boolean newMark)

Unconditionally sets the value of both the reference and mark.

Parameters:: newReference - the new value for the reference; newMark - the new value for the mark

weakCompareAndSet

public boolean weakCompareAndSet(Object expectedReference,
                                 Object newReference,
                                 boolean expectedMark,
                                 boolean newMark)

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; expectedMark - the expected value of the mark; newMark - the new value for the mark
Returns:: true if successful