AtomicReferenceFieldUpdater JDK 1.6)

Description

publicabstract abstract class AtomicReferenceFieldUpdater

A reflection-based utility that enables atomic updates to designated volatile reference fields of designated classes.

A reflection-based utility that enables atomic updates to designated volatile reference fields of designated classes. This class is designed for use in atomic data structures in which several reference fields of the same node are independently subject to atomic updates. For example, a tree node might be declared as

 class Node {
   private volatile Node left, right;

   private static final AtomicReferenceFieldUpdater<Node, Node> leftUpdater =
     AtomicReferenceFieldUpdater.newUpdater(Node.class, Node.class, "left");
   private static AtomicReferenceFieldUpdater<Node, Node> rightUpdater =
     AtomicReferenceFieldUpdater.newUpdater(Node.class, Node.class, "right");

   Node getLeft() { return left;  }
   boolean compareAndSetLeft(Node expect, Node update) {
     return leftUpdater.compareAndSet(this, expect, update);
   }
   // ... and so on
 }

Note that the guarantees of the compareAndSet method in this class are weaker than in other atomic classes. Because this class cannot ensure that all uses of the field are appropriate for purposes of atomic access, it can guarantee atomicity only with respect to other invocations of compareAndSet and set on the same updater.

See also:

Methods

Hide/Show inherited methods

publicabstract boolean compareAndSet ( T obj, V expect, V update)

Atomically sets the field of the given object managed by this updater to the given updated value if the current value == the expected value.

Atomically sets the field of the given object managed by this updater
to the given updated value if the current value == the
expected value. This method is guaranteed to be atomic with respect to
other calls to compareAndSet and set, but not
necessarily with respect to other changes in the field.
Returns: true if successful.
Parameters:
- obj - An object whose field to conditionally set
- expect - the expected value
- update - the new value

publicabstract V get ( T obj)

Gets the current value held in the field of the given object managed by this updater.

public V getAndSet ( T obj, V newValue)

Atomically sets the field of the given object managed by this updater to the given value and returns the old value.

publicabstract void lazySet ( T obj, V newValue)

Eventually sets the field of the given object managed by this updater to the given updated value.

publicstatic AtomicReferenceFieldUpdater< U, W> newUpdater (Class< U> tclass, Class< W> vclass, String fieldName)

Creates and returns an updater for objects with the given field.

publicabstract void set ( T obj, V newValue)

Sets the field of the given object managed by this updater to the given updated value.

Sets the field of the given object managed by this updater to the
given updated value. This operation is guaranteed to act as a volatile
store with respect to subsequent invocations of compareAndSet.
Parameters:
- obj - An object whose field to set
- newValue - the new value

publicabstract boolean weakCompareAndSet ( T obj, V expect, V update)

Atomically sets the field of the given object managed by this updater to the given updated value if the current value == the expected value.

May fail spuriously and does not provide ordering guarantees, so is only rarely an appropriate alternative to compareAndSet.
Returns: true if successful.
Parameters:
- obj - An object whose field to conditionally set
- expect - the expected value
- update - the new value