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

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

Since:

1.5

Constructor Summary

protected

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

Method Summary

int	addAndGet(T obj, int delta) Atomically add the given value to current value.
abstract boolean	compareAndSet(T obj, int expect, int 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.
int	decrementAndGet(T obj) Atomically decrement by one the current value.
abstract int	get(T obj) Get the current value held in the field by the given object.
int	getAndAdd(T obj, int delta) Atomically add the given value to current value.
int	getAndDecrement(T obj) Atomically decrement by one the current value.
int	getAndIncrement(T obj) Atomically increment by one the current value.
int	getAndSet(T obj, int newValue) Set to the given value and return the old value.
int	incrementAndGet(T obj) Atomically increment by one the current value.
static <U> AtomicIntegerFieldUpdater<U>	newUpdater(Class<U> tclass, String fieldName) Creates an updater for objects with the given field.
abstract void	set(T obj, int newValue) Set the field of the given object managed by this updater.
abstract boolean	weakCompareAndSet(T obj, int expect, int 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

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 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 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.

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 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.

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)

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

public abstract int 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

public int getAndSet(T obj,
                     int 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

getAndIncrement

public int getAndIncrement(T obj)

Atomically increment by one the current value.

Parameters:

obj - An object whose field to get and set

Returns:

the previous value;

getAndDecrement

public int getAndDecrement(T obj)

Atomically decrement by one the current value.

Parameters:

obj - An object whose field to get and set

Returns:

the previous value;

getAndAdd

public int getAndAdd(T obj,
                     int delta)

Atomically add the given value to current value.

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 increment by one the current value.

Parameters:

obj - An object whose field to get and set

Returns:

the updated value;

decrementAndGet

public int decrementAndGet(T obj)

Atomically decrement by one the current value.

Parameters:

obj - An object whose field to get and set

Returns:

the updated value;

addAndGet

public int addAndGet(T obj,
                     int delta)

Atomically add the given value to current value.

Parameters:

obj - An object whose field to get and set

delta - the value to add

Returns:

the updated value;