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 only with respect to other invocations of compareAndSet and set on the same updater.

Since:

1.5

Author:

Doug Lea

Constructor Summary

Constructors

Modifier	Constructor and Description
protected	AtomicIntegerFieldUpdater() Protected do-nothing constructor for use by subclasses.

Method Summary

Methods

Modifier and Type	Method and Description
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