java.util.concurrent.atomic
Class AtomicReferenceFieldUpdater<T,V>

java.lang.Object sample code for java.lang.Object definition code for java.lang.Object 
  extended by java.util.concurrent.atomic.AtomicReferenceFieldUpdater<T,V>
Type Parameters:
T - The type of the object holding the updatable field
V - The type of the field

public abstract class AtomicReferenceFieldUpdater<T,V>
extends Object sample code for java.lang.Object definition code for java.lang.Object

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 and volatile semantics only with respect to other invocations of compareAndSet and set.

Since:
1.5

Constructor Summary
protected AtomicReferenceFieldUpdater sample code for java.util.concurrent.atomic.AtomicReferenceFieldUpdater.AtomicReferenceFieldUpdater() definition code for java.util.concurrent.atomic.AtomicReferenceFieldUpdater.AtomicReferenceFieldUpdater() ()
          Protected do-nothing constructor for use by subclasses.
 
Method Summary
abstract  boolean compareAndSet sample code for java.util.concurrent.atomic.AtomicReferenceFieldUpdater.compareAndSet(T, V, V) definition code for java.util.concurrent.atomic.AtomicReferenceFieldUpdater.compareAndSet(T, V, V) (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.
abstract  V get sample code for java.util.concurrent.atomic.AtomicReferenceFieldUpdater.get(T) definition code for java.util.concurrent.atomic.AtomicReferenceFieldUpdater.get(T) (T obj)
          Get the current value held in the field by the given object.
 V getAndSet sample code for java.util.concurrent.atomic.AtomicReferenceFieldUpdater.getAndSet(T, V) definition code for java.util.concurrent.atomic.AtomicReferenceFieldUpdater.getAndSet(T, V) (T obj, V newValue)
          Set to the given value and return the old value.
static
<U,W> AtomicReferenceFieldUpdater sample code for java.util.concurrent.atomic.AtomicReferenceFieldUpdater definition code for java.util.concurrent.atomic.AtomicReferenceFieldUpdater <U,W>
newUpdater sample code for java.util.concurrent.atomic.AtomicReferenceFieldUpdater.newUpdater(java.lang.Class, java.lang.Class, java.lang.String) definition code for java.util.concurrent.atomic.AtomicReferenceFieldUpdater.newUpdater(java.lang.Class, java.lang.Class, java.lang.String) (Class sample code for java.lang.Class definition code for java.lang.Class <U> tclass, Class sample code for java.lang.Class definition code for java.lang.Class <W> vclass, String sample code for java.lang.String definition code for java.lang.String  fieldName)
          Creates an updater for objects with the given field.
abstract  void set sample code for java.util.concurrent.atomic.AtomicReferenceFieldUpdater.set(T, V) definition code for java.util.concurrent.atomic.AtomicReferenceFieldUpdater.set(T, V) (T obj, V newValue)
          Set the field of the given object managed by this updater.
abstract  boolean weakCompareAndSet sample code for java.util.concurrent.atomic.AtomicReferenceFieldUpdater.weakCompareAndSet(T, V, V) definition code for java.util.concurrent.atomic.AtomicReferenceFieldUpdater.weakCompareAndSet(T, V, V) (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.
 
Methods inherited from class java.lang.Object sample code for java.lang.Object definition code for java.lang.Object
clone sample code for java.lang.Object.clone() definition code for java.lang.Object.clone() , equals sample code for java.lang.Object.equals(java.lang.Object) definition code for java.lang.Object.equals(java.lang.Object) , finalize sample code for java.lang.Object.finalize() definition code for java.lang.Object.finalize() , getClass sample code for java.lang.Object.getClass() definition code for java.lang.Object.getClass() , hashCode sample code for java.lang.Object.hashCode() definition code for java.lang.Object.hashCode() , notify sample code for java.lang.Object.notify() definition code for java.lang.Object.notify() , notifyAll sample code for java.lang.Object.notifyAll() definition code for java.lang.Object.notifyAll() , toString sample code for java.lang.Object.toString() definition code for java.lang.Object.toString() , wait sample code for java.lang.Object.wait() definition code for java.lang.Object.wait() , wait sample code for java.lang.Object.wait(long) definition code for java.lang.Object.wait(long) , wait sample code for java.lang.Object.wait(long, int) definition code for java.lang.Object.wait(long, int)
 

Constructor Detail

AtomicReferenceFieldUpdater sample code for java.util.concurrent.atomic.AtomicReferenceFieldUpdater() definition code for java.util.concurrent.atomic.AtomicReferenceFieldUpdater()

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

Method Detail

newUpdater sample code for java.util.concurrent.atomic.AtomicReferenceFieldUpdater.<U, W>newUpdater(java.lang.Class<U>, java.lang.Class<W>, java.lang.String) definition code for java.util.concurrent.atomic.AtomicReferenceFieldUpdater.<U, W>newUpdater(java.lang.Class<U>, java.lang.Class<W>, java.lang.String)

public static <U,W> AtomicReferenceFieldUpdater sample code for java.util.concurrent.atomic.AtomicReferenceFieldUpdater definition code for java.util.concurrent.atomic.AtomicReferenceFieldUpdater <U,W> newUpdater(Class sample code for java.lang.Class definition code for java.lang.Class <U> tclass,
                                                                Class sample code for java.lang.Class definition code for java.lang.Class <W> vclass,
                                                                String sample code for java.lang.String definition code for 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.

Parameters:
tclass - the class of the objects holding the field.
vclass - the class of the field
fieldName - the name of the field to be updated.
Returns:
the updater
Throws:
IllegalArgumentException sample code for java.lang.IllegalArgumentException definition code for java.lang.IllegalArgumentException - if the field is not a volatile reference type.
RuntimeException sample code for java.lang.RuntimeException definition code for java.lang.RuntimeException - with a nested reflection-based exception if the class does not hold field or is the wrong type.

compareAndSet sample code for java.util.concurrent.atomic.AtomicReferenceFieldUpdater.compareAndSet(T, V, V) definition code for java.util.concurrent.atomic.AtomicReferenceFieldUpdater.compareAndSet(T, V, V)

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.

Parameters:
obj - An object whose field to conditionally set
expect - the expected value
update - the new value
Returns:
true if successful.

weakCompareAndSet sample code for java.util.concurrent.atomic.AtomicReferenceFieldUpdater.weakCompareAndSet(T, V, V) definition code for java.util.concurrent.atomic.AtomicReferenceFieldUpdater.weakCompareAndSet(T, V, V)

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.

Parameters:
obj - An object whose field to conditionally set
expect - the expected value
update - the new value
Returns:
true if successful.

set sample code for java.util.concurrent.atomic.AtomicReferenceFieldUpdater.set(T, V) definition code for java.util.concurrent.atomic.AtomicReferenceFieldUpdater.set(T, V)

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.

Parameters:
obj - An object whose field to set
newValue - the new value

get sample code for java.util.concurrent.atomic.AtomicReferenceFieldUpdater.get(T) definition code for java.util.concurrent.atomic.AtomicReferenceFieldUpdater.get(T)

public abstract V get(T obj)
Get the current value held in the field by the given object.

Parameters:
obj - An object whose field to get
Returns:
the current value

getAndSet sample code for java.util.concurrent.atomic.AtomicReferenceFieldUpdater.getAndSet(T, V) definition code for java.util.concurrent.atomic.AtomicReferenceFieldUpdater.getAndSet(T, V)

public V getAndSet(T obj,
                   V newValue)
Set to the given value and return the old value.

Parameters:
obj - An object whose field to get and set
newValue - the new value
Returns:
the previous value