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


java.lang.Object
  extended by 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
          Creates a new AtomicStampedReference with the given initial values.
 
Method Summary
 boolean attemptStamp ( V
          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
          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
          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. 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
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) 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