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


java.lang.Object
  extended by java.util.concurrent.atomic.AtomicMarkableReference<V>
Type Parameters:
V - The type of object referred to by this reference
public class AtomicMarkableReference<V>
extends Object

An 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.

Since:
1.5

Constructor Summary
AtomicMarkableReference ( V
          Creates a new AtomicMarkableReference with the given initial values.
 
Method Summary
 boolean attemptMark ( V
          Atomically sets the value of the mark to the given update value if the current reference is == to the expected reference.
 boolean compareAndSet ( V  expectedReference, V
          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.
  V get (boolean[] markHolder)
          Returns the current values of both the reference and the mark.
  V getReference ()
          Returns the current value of the reference.
 boolean isMarked ()
          Returns the current value of the mark.
 void set ( V  newReference, boolean newMark)
          Unconditionally sets the value of both the reference and mark.
 boolean weakCompareAndSet ( V  expectedReference, V
          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(V initialRef,
                               boolean initialMark)
Creates a new AtomicMarkableReference with the given initial values.

Parameters:
initialRef - the initial reference
initialMark - the initial mark
Method Detail

getReference


public V 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

get


public V get(boolean[] markHolder)
Returns the current values of both the reference and the mark. Typical usage is boolean[1] holder; ref = v.get(holder); .

Parameters:
markHolder - an array of size of at least one. On return, markholder[0] will hold the value of the mark.
Returns:
the current value of the reference

weakCompareAndSet


public boolean weakCompareAndSet(V expectedReference,
                                 V 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. 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.

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

compareAndSet


public boolean compareAndSet(V expectedReference,
                             V 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.

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

set


public void set(V 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

attemptMark


public boolean attemptMark(V expectedReference,
                           boolean newMark)
Atomically sets the value of the mark to the given update value if the current reference is == to the expected reference. Any given invocation of this operation may fail (return false) 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