Java™ Platform
Standard Ed. 6

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

java.lang.Object
  extended by java.util.concurrent.atomic.AtomicIntegerFieldUpdater<T>
Type Parameters:
T - The type of the object holding the updatable field

public abstract class AtomicIntegerFieldUpdater<T>
extends Object

A reflection-based utility that enables atomic updates to designated volatile int 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 AtomicIntegerFieldUpdater()
          Protected do-nothing constructor for use by subclasses.
 
Method Summary
 int addAndGet(T obj, int 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, int expect, int 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.
 int decrementAndGet(T obj)
          Atomically decrements by one the current value of the field of the given object managed by this updater.
abstract  int get(T obj)
          Gets the current value held in the field of the given object managed by this updater.
 int getAndAdd(T obj, int delta)
          Atomically adds the given value to the current value of the field of the given object managed by this updater.
 int getAndDecrement(T obj)
          Atomically decrements by one the current value of the field of the given object managed by this updater.
 int getAndIncrement(T obj)
          Atomically increments by one the current value of the field of the given object managed by this updater.
 int getAndSet(T obj, int newValue)
          Atomically sets the field of the given object managed by this updater to the given value and returns the old value.
 int 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, int newValue)
          Eventually sets the field of the given object managed by this updater to the given updated value.
static
<U> AtomicIntegerFieldUpdater<U>
newUpdater(Class<U> tclass, String fieldName)
          Creates and returns an updater for objects with the given field.
abstract  void set(T obj, int newValue)
          Sets the field of the given object managed by this updater to the given updated value.
abstract  boolean weakCompareAndSet(T obj, int expect, int 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 Detail

AtomicIntegerFieldUpdater

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

Method Detail

newUpdater

public static <U> AtomicIntegerFieldUpdater<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 integer 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,
                                      int expect,
                                      int 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,
                                          int expect,
                                          int 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.

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,
                         int 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,
                             int 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 int 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 int getAndSet(T obj,
                     int 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 int 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 int 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 int getAndAdd(T obj,
                     int 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 int incrementAndGet(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 updated value

decrementAndGet

public int decrementAndGet(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 updated value

addAndGet

public int addAndGet(T obj,
                     int 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 updated value

Java™ Platform
Standard Ed. 6

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