File	Doc	Category	Size	Date	Package
AtomicReferenceFieldUpdater.java	API Doc	Java SE 5 API	8587	Fri Aug 26 14:57:26 BST 2005	java.util.concurrent.atomic

AtomicReferenceFieldUpdater

• java.lang.Object

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
}

Fields Summary

Constructors Summary
protected AtomicReferenceFieldUpdater() Protected do-nothing constructor for use by subclasses.

Methods Summary
public abstract boolean	compareAndSet(T obj, V expect, V update) Atomically set the value of 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. param obj An object whose field to conditionally set param expect the expected value param update the new value return true if successful.
public abstract V	get(T obj) Get the current value held in the field by the given object. param obj An object whose field to get return the current value
public V	getAndSet(T obj, V newValue) Set to the given value and return the old value. param obj An object whose field to get and set param newValue the new value return the previous value for (;;) { V current = get(obj); if (compareAndSet(obj, current, newValue)) return current; }
public static java.util.concurrent.atomic.AtomicReferenceFieldUpdater	newUpdater(java.lang.Class tclass, java.lang.Class vclass, java.lang.String fieldName) Creates an updater for objects with the given field. The Class arguments are needed to check that reflective types and generic types match. param tclass the class of the objects holding the field. param vclass the class of the field param fieldName the name of the field to be updated. return the updater throws IllegalArgumentException if the field is not a volatile reference type. throws RuntimeException with a nested reflection-based exception if the class does not hold field or is the wrong type. // Currently rely on standard intrinsics implementation return new AtomicReferenceFieldUpdaterImpl<U,W>(tclass, vclass, fieldName);
public abstract void	set(T obj, V newValue) Set the field of the given object managed by this updater. This operation is guaranteed to act as a volatile store with respect to subsequent invocations of compareAndSet. param obj An object whose field to set param newValue the new value
public abstract boolean	weakCompareAndSet(T obj, V expect, V update) Atomically set the value of 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, and may fail spuriously. param obj An object whose field to conditionally set param expect the expected value param update the new value return true if successful.