AtomicReferenceFieldUpdater (Java SE 9 & JDK 9 ) (original) (raw)

java.lang.Object
- 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
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 only with respect to other invocations ofcompareAndSet and set on the same updater.
Object arguments for parameters of type T that are not instances of the class passed to newUpdater(java.lang.Class, java.lang.Class, java.lang.String) will result in a ClassCastException being thrown.
Since:
1.5

Constructor Summary

Constructors

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

Method Summary

All Methods Static Methods Instance Methods Abstract Methods Concrete Methods

Modifier and Type	Method	Description
V	accumulateAndGet(T obj,V x,BinaryOperator<V> accumulatorFunction)	Atomically updates (with memory effects as specified by VarHandle.compareAndSet(java.lang.Object...)) the field of the given object managed by this updater with the results of applying the given function to the current and given values, returning the updated value.
abstract boolean	compareAndSet(T obj,V expect,V 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.
abstract V	get(T obj)	Returns the current value held in the field of the given object managed by this updater.
V	getAndAccumulate(T obj,V x,BinaryOperator<V> accumulatorFunction)	Atomically updates (with memory effects as specified by VarHandle.compareAndSet(java.lang.Object...)) the field of the given object managed by this updater with the results of applying the given function to the current and given values, returning the previous value.
V	getAndSet(T obj,V newValue)	Atomically sets the field of the given object managed by this updater to the given value and returns the old value.
V	getAndUpdate(T obj,UnaryOperator<V> updateFunction)	Atomically updates (with memory effects as specified by VarHandle.compareAndSet(java.lang.Object...)) the field of the given object managed by this updater with the results of applying the given function, returning the previous value.
abstract void	lazySet(T obj,V newValue)	Eventually sets the field of the given object managed by this updater to the given updated value.
static <U,W> AtomicReferenceFieldUpdater<U,W>	newUpdater(Class tclass,Class vclass,String fieldName)	Creates and returns an updater for objects with the given field.
abstract void	set(T obj,V newValue)	Sets the field of the given object managed by this updater to the given updated value.
V	updateAndGet(T obj,UnaryOperator<V> updateFunction)	Atomically updates (with memory effects as specified by VarHandle.compareAndSet(java.lang.Object...)) the field of the given object managed by this updater with the results of applying the given function, returning the updated value.
abstract boolean	weakCompareAndSet(T obj,V expect,V 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](../../../../java/lang/Object.html "class in java.lang")  
   `[clone](../../../../java/lang/Object.html#clone--), [equals](../../../../java/lang/Object.html#equals-java.lang.Object-), [finalize](../../../../java/lang/Object.html#finalize--), [getClass](../../../../java/lang/Object.html#getClass--), [hashCode](../../../../java/lang/Object.html#hashCode--), [notify](../../../../java/lang/Object.html#notify--), [notifyAll](../../../../java/lang/Object.html#notifyAll--), [toString](../../../../java/lang/Object.html#toString--), [wait](../../../../java/lang/Object.html#wait--), [wait](../../../../java/lang/Object.html#wait-long-), [wait](../../../../java/lang/Object.html#wait-long-int-)`

Constructor Detail

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

Method Detail

* #### newUpdater  
public static <U,W> [AtomicReferenceFieldUpdater](../../../../java/util/concurrent/atomic/AtomicReferenceFieldUpdater.html "class in java.util.concurrent.atomic")<U,W> newUpdater([Class](../../../../java/lang/Class.html "class in java.lang")<U> tclass,  
                                                                [Class](../../../../java/lang/Class.html "class in java.lang")<W> vclass,  
                                                                [String](../../../../java/lang/String.html "class in java.lang") fieldName)  
Creates and returns an updater for objects with the given field. The Class arguments are needed to check that reflective types and generic types match.  
Type Parameters:  
`U` \- the type of instances of tclass  
`W` \- the type of instances of vclass  
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:  
`[ClassCastException](../../../../java/lang/ClassCastException.html "class in java.lang")` \- if the field is of the wrong type  
`[IllegalArgumentException](../../../../java/lang/IllegalArgumentException.html "class in java.lang")` \- if the field is not volatile  
`[RuntimeException](../../../../java/lang/RuntimeException.html "class in java.lang")` \- with a nested reflection-based exception if the class does not hold field or is the wrong type, or the field is inaccessible to the caller according to Java language access control  
* #### compareAndSet  
public abstract boolean compareAndSet([T](../../../../java/util/concurrent/atomic/AtomicReferenceFieldUpdater.html "type parameter in AtomicReferenceFieldUpdater") obj,  
                                      [V](../../../../java/util/concurrent/atomic/AtomicReferenceFieldUpdater.html "type parameter in AtomicReferenceFieldUpdater") expect,  
                                      [V](../../../../java/util/concurrent/atomic/AtomicReferenceFieldUpdater.html "type parameter in AtomicReferenceFieldUpdater") 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  
* #### weakCompareAndSet  
public abstract boolean weakCompareAndSet([T](../../../../java/util/concurrent/atomic/AtomicReferenceFieldUpdater.html "type parameter in AtomicReferenceFieldUpdater") obj,  
                                          [V](../../../../java/util/concurrent/atomic/AtomicReferenceFieldUpdater.html "type parameter in AtomicReferenceFieldUpdater") expect,  
                                          [V](../../../../java/util/concurrent/atomic/AtomicReferenceFieldUpdater.html "type parameter in AtomicReferenceFieldUpdater") 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](package-summary.html#weakCompareAndSet), 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  
* #### set  
public abstract void set([T](../../../../java/util/concurrent/atomic/AtomicReferenceFieldUpdater.html "type parameter in AtomicReferenceFieldUpdater") obj,  
                         [V](../../../../java/util/concurrent/atomic/AtomicReferenceFieldUpdater.html "type parameter in AtomicReferenceFieldUpdater") 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](../../../../java/util/concurrent/atomic/AtomicReferenceFieldUpdater.html "type parameter in AtomicReferenceFieldUpdater") obj,  
                             [V](../../../../java/util/concurrent/atomic/AtomicReferenceFieldUpdater.html "type parameter in AtomicReferenceFieldUpdater") 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 [V](../../../../java/util/concurrent/atomic/AtomicReferenceFieldUpdater.html "type parameter in AtomicReferenceFieldUpdater") get([T](../../../../java/util/concurrent/atomic/AtomicReferenceFieldUpdater.html "type parameter in AtomicReferenceFieldUpdater") obj)  
Returns 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 [V](../../../../java/util/concurrent/atomic/AtomicReferenceFieldUpdater.html "type parameter in AtomicReferenceFieldUpdater") getAndSet([T](../../../../java/util/concurrent/atomic/AtomicReferenceFieldUpdater.html "type parameter in AtomicReferenceFieldUpdater") obj,  
                   [V](../../../../java/util/concurrent/atomic/AtomicReferenceFieldUpdater.html "type parameter in AtomicReferenceFieldUpdater") 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  
* #### getAndUpdate  
public final [V](../../../../java/util/concurrent/atomic/AtomicReferenceFieldUpdater.html "type parameter in AtomicReferenceFieldUpdater") getAndUpdate([T](../../../../java/util/concurrent/atomic/AtomicReferenceFieldUpdater.html "type parameter in AtomicReferenceFieldUpdater") obj,  
                            [UnaryOperator](../../../../java/util/function/UnaryOperator.html "interface in java.util.function")<[V](../../../../java/util/concurrent/atomic/AtomicReferenceFieldUpdater.html "type parameter in AtomicReferenceFieldUpdater")> updateFunction)  
Atomically updates (with memory effects as specified by [VarHandle.compareAndSet(java.lang.Object...)](../../../../java/lang/invoke/VarHandle.html#compareAndSet-java.lang.Object...-)) the field of the given object managed by this updater with the results of applying the given function, returning the previous value. The function should be side-effect-free, since it may be re-applied when attempted updates fail due to contention among threads.  
Parameters:  
`obj` \- An object whose field to get and set  
`updateFunction` \- a side-effect-free function  
Returns:  
the previous value  
Since:  
1.8  
* #### updateAndGet  
public final [V](../../../../java/util/concurrent/atomic/AtomicReferenceFieldUpdater.html "type parameter in AtomicReferenceFieldUpdater") updateAndGet([T](../../../../java/util/concurrent/atomic/AtomicReferenceFieldUpdater.html "type parameter in AtomicReferenceFieldUpdater") obj,  
                            [UnaryOperator](../../../../java/util/function/UnaryOperator.html "interface in java.util.function")<[V](../../../../java/util/concurrent/atomic/AtomicReferenceFieldUpdater.html "type parameter in AtomicReferenceFieldUpdater")> updateFunction)  
Atomically updates (with memory effects as specified by [VarHandle.compareAndSet(java.lang.Object...)](../../../../java/lang/invoke/VarHandle.html#compareAndSet-java.lang.Object...-)) the field of the given object managed by this updater with the results of applying the given function, returning the updated value. The function should be side-effect-free, since it may be re-applied when attempted updates fail due to contention among threads.  
Parameters:  
`obj` \- An object whose field to get and set  
`updateFunction` \- a side-effect-free function  
Returns:  
the updated value  
Since:  
1.8  
* #### getAndAccumulate  
public final [V](../../../../java/util/concurrent/atomic/AtomicReferenceFieldUpdater.html "type parameter in AtomicReferenceFieldUpdater") getAndAccumulate([T](../../../../java/util/concurrent/atomic/AtomicReferenceFieldUpdater.html "type parameter in AtomicReferenceFieldUpdater") obj,  
                                [V](../../../../java/util/concurrent/atomic/AtomicReferenceFieldUpdater.html "type parameter in AtomicReferenceFieldUpdater") x,  
                                [BinaryOperator](../../../../java/util/function/BinaryOperator.html "interface in java.util.function")<[V](../../../../java/util/concurrent/atomic/AtomicReferenceFieldUpdater.html "type parameter in AtomicReferenceFieldUpdater")> accumulatorFunction)  
Atomically updates (with memory effects as specified by [VarHandle.compareAndSet(java.lang.Object...)](../../../../java/lang/invoke/VarHandle.html#compareAndSet-java.lang.Object...-)) the field of the given object managed by this updater with the results of applying the given function to the current and given values, returning the previous value. The function should be side-effect-free, since it may be re-applied when attempted updates fail due to contention among threads. The function is applied with the current value as its first argument, and the given update as the second argument.  
Parameters:  
`obj` \- An object whose field to get and set  
`x` \- the update value  
`accumulatorFunction` \- a side-effect-free function of two arguments  
Returns:  
the previous value  
Since:  
1.8  
* #### accumulateAndGet  
public final [V](../../../../java/util/concurrent/atomic/AtomicReferenceFieldUpdater.html "type parameter in AtomicReferenceFieldUpdater") accumulateAndGet([T](../../../../java/util/concurrent/atomic/AtomicReferenceFieldUpdater.html "type parameter in AtomicReferenceFieldUpdater") obj,  
                                [V](../../../../java/util/concurrent/atomic/AtomicReferenceFieldUpdater.html "type parameter in AtomicReferenceFieldUpdater") x,  
                                [BinaryOperator](../../../../java/util/function/BinaryOperator.html "interface in java.util.function")<[V](../../../../java/util/concurrent/atomic/AtomicReferenceFieldUpdater.html "type parameter in AtomicReferenceFieldUpdater")> accumulatorFunction)  
Atomically updates (with memory effects as specified by [VarHandle.compareAndSet(java.lang.Object...)](../../../../java/lang/invoke/VarHandle.html#compareAndSet-java.lang.Object...-)) the field of the given object managed by this updater with the results of applying the given function to the current and given values, returning the updated value. The function should be side-effect-free, since it may be re-applied when attempted updates fail due to contention among threads. The function is applied with the current value as its first argument, and the given update as the second argument.  
Parameters:  
`obj` \- An object whose field to get and set  
`x` \- the update value  
`accumulatorFunction` \- a side-effect-free function of two arguments  
Returns:  
the updated value  
Since:  
1.8

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AtomicReferenceFieldUpdater (Java SE 9 & JDK 9 ) (original) (raw)

Constructor Summary

Method Summary

Constructor Detail

Method Detail