AtomicLongFieldUpdater (Java Platform SE 6) - JDK 5 Documentation v6.0, Java 2 SDK 英文文档

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Java™ Platform
Standard Ed. 6

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java.util.concurrent.atomic
Class AtomicLongFieldUpdater<T>

java.lang.Object
  java.util.concurrent.atomic.AtomicLongFieldUpdater<T>


Type Parameters:: T - The type of the object holding the updatable field

public abstract class AtomicLongFieldUpdater<T>
extends Object
extends Object

A reflection-based utility that enables atomic updates to designated volatile long fields of designated classes. This class is designed for use in atomic data structures in which several fields of the same node are independently subject to atomic updates.

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.

Since:: 1.5

Constructor Summary

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

Method Summary

long addAndGet(T obj, long delta)
          Atomically adds the given value to the current value of the field of the given object managed by this updater.

abstract boolean compareAndSet(T obj, long expect, long 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.

long decrementAndGet(T obj)
          Atomically decrements by one the current value of the field of the given object managed by this updater.

abstract long get(T obj)
          Gets the current value held in the field of the given object managed by this updater.

long getAndAdd(T obj, long delta)
          Atomically adds the given value to the current value of the field of the given object managed by this updater.

long getAndDecrement(T obj)
          Atomically decrements by one the current value of the field of the given object managed by this updater.

long getAndIncrement(T obj)
          Atomically increments by one the current value of the field of the given object managed by this updater.

long getAndSet(T obj, long newValue)
          Atomically sets the field of the given object managed by this updater to the given value and returns the old value.

long incrementAndGet(T obj)
          Atomically increments by one the current value of the field of the given object managed by this updater.

abstract void lazySet(T obj, long newValue)
          Eventually sets the field of the given object managed by this updater to the given updated value.

static <U> AtomicLongFieldUpdater<U> newUpdater(Class<U> tclass, String fieldName)
          Creates and returns an updater for objects with the given field.

abstract void set(T obj, long newValue)
          Sets the field of the given object managed by this updater to the given updated value.

abstract boolean weakCompareAndSet(T obj, long expect, long 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.

Methods inherited from class java.lang.Object

clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

Constructor Summary
`protected`	`AtomicLongFieldUpdater()` Protected do-nothing constructor for use by subclasses.

Methods inherited from class java.lang.Object
`clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait`

Constructor Detail

AtomicLongFieldUpdater

protected AtomicLongFieldUpdater()

Protected do-nothing constructor for use by subclasses.

Method Detail

newUpdater

public static <U> AtomicLongFieldUpdater<U> newUpdater(Class<U> tclass,
                                                       String fieldName)

Creates and returns an updater for objects with the given field. The Class argument is needed to check that reflective types and generic types match.

Parameters:: tclass - the class of the objects holding the field; fieldName - the name of the field to be updated.
Returns:: the updater
Throws:: IllegalArgumentException - if the field is not a volatile long type.; RuntimeException - with a nested reflection-based exception if the class does not hold field or is the wrong type.

compareAndSet

public abstract boolean compareAndSet(T obj,
                                      long expect,
                                      long 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. 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.
Throws:: ClassCastException - if obj is not an instance of the class possessing the field established in the constructor.

weakCompareAndSet

public abstract boolean weakCompareAndSet(T obj,
                                          long expect,
                                          long update)

May fail spuriously and does not provide ordering guarantees, so is only rarely an appropriate alternative to compareAndSet.

Parameters:: obj - An object whose field to conditionally set; expect - the expected value; update - the new value
Returns:: true if successful.
Throws:: ClassCastException - if obj is not an instance of the class possessing the field established in the constructor.

set

public abstract void set(T obj,
                         long newValue)

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

lazySet

public abstract void lazySet(T obj,
                             long newValue)

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

Parameters:: obj - An object whose field to set; newValue - the new value
Since:: 1.6

get

public abstract long get(T obj)

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

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

getAndSet

public long getAndSet(T obj,
                      long newValue)

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

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

getAndIncrement

public long getAndIncrement(T obj)

Atomically increments by one the current value of the field of the given object managed by this updater.

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

getAndDecrement

public long getAndDecrement(T obj)

Atomically decrements by one the current value of the field of the given object managed by this updater.

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

getAndAdd

public long getAndAdd(T obj,
                      long delta)

Atomically adds the given value to the current value of the field of the given object managed by this updater.

Parameters:: obj - An object whose field to get and set; delta - the value to add
Returns:: the previous value

incrementAndGet

public long incrementAndGet(T obj)