Added in [API level 1](https://developer.android.com/guide/topics/manifest/uses-sdk-element#ApiLevels) Summary: [Protected Ctors](https://developer.android.com/reference/java/util/concurrent/atomic/AtomicReferenceFieldUpdater#proctors) \| [Methods](https://developer.android.com/reference/java/util/concurrent/atomic/AtomicReferenceFieldUpdater#pubmethods) \| [Inherited Methods](https://developer.android.com/reference/java/util/concurrent/atomic/AtomicReferenceFieldUpdater#inhmethods)

# AtomicReferenceFieldUpdater


`
public


abstract
class
AtomicReferenceFieldUpdater
`


`

extends https://developer.android.com/reference/java/lang/Object


`

`


`

|---|---|
| [java.lang.Object](https://developer.android.com/reference/java/lang/Object) ||
| ↳ | java.util.concurrent.atomic.AtomicReferenceFieldUpdater\<T, V\> |

<br />

*** ** * ** ***

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 final 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 of
`compareAndSet` and `set` on the same updater.

Object arguments for parameters of type `T` that are not
instances of the class passed to `https://developer.android.com/reference/java/util/concurrent/atomic/AtomicReferenceFieldUpdater#newUpdater(java.lang.Class<U>,%20java.lang.Class<W>,%20java.lang.String)` will result in
a `https://developer.android.com/reference/java/lang/ClassCastException` being thrown.

## Summary

| ### Protected constructors ||
|---|---|
| ` https://developer.android.com/reference/java/util/concurrent/atomic/AtomicReferenceFieldUpdater#AtomicReferenceFieldUpdater()() ` Protected do-nothing constructor for use by subclasses. |

| ### Public methods ||
|---|---|
| ` final V` | ` https://developer.android.com/reference/java/util/concurrent/atomic/AtomicReferenceFieldUpdater#accumulateAndGet(T,%20V,%20java.util.function.BinaryOperator<V>)(T obj, V x, https://developer.android.com/reference/java/util/function/BinaryOperator<V> accumulatorFunction) ` Atomically updates (with memory effects as specified by `https://developer.android.com/reference/java/lang/invoke/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` | ` https://developer.android.com/reference/java/util/concurrent/atomic/AtomicReferenceFieldUpdater#compareAndSet(T,%20V,%20V)(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` | ` https://developer.android.com/reference/java/util/concurrent/atomic/AtomicReferenceFieldUpdater#get(T)(T obj) ` Returns the current value held in the field of the given object managed by this updater. |
| ` final V` | ` https://developer.android.com/reference/java/util/concurrent/atomic/AtomicReferenceFieldUpdater#getAndAccumulate(T,%20V,%20java.util.function.BinaryOperator<V>)(T obj, V x, https://developer.android.com/reference/java/util/function/BinaryOperator<V> accumulatorFunction) ` Atomically updates (with memory effects as specified by `https://developer.android.com/reference/java/lang/invoke/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` | ` https://developer.android.com/reference/java/util/concurrent/atomic/AtomicReferenceFieldUpdater#getAndSet(T,%20V)(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. |
| ` final V` | ` https://developer.android.com/reference/java/util/concurrent/atomic/AtomicReferenceFieldUpdater#getAndUpdate(T,%20java.util.function.UnaryOperator<V>)(T obj, https://developer.android.com/reference/java/util/function/UnaryOperator<V> updateFunction) ` Atomically updates (with memory effects as specified by `https://developer.android.com/reference/java/lang/invoke/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` | ` https://developer.android.com/reference/java/util/concurrent/atomic/AtomicReferenceFieldUpdater#lazySet(T,%20V)(T obj, V newValue) ` Eventually sets the field of the given object managed by this updater to the given updated value. |
| ` static <U, W> https://developer.android.com/reference/java/util/concurrent/atomic/AtomicReferenceFieldUpdater<U, W>` | ` https://developer.android.com/reference/java/util/concurrent/atomic/AtomicReferenceFieldUpdater#newUpdater(java.lang.Class<U>,%20java.lang.Class<W>,%20java.lang.String)(https://developer.android.com/reference/java/lang/Class<U> tclass, https://developer.android.com/reference/java/lang/Class<W> vclass, https://developer.android.com/reference/java/lang/String fieldName) ` Creates and returns an updater for objects with the given field. |
| ` abstract void` | ` https://developer.android.com/reference/java/util/concurrent/atomic/AtomicReferenceFieldUpdater#set(T,%20V)(T obj, V newValue) ` Sets the field of the given object managed by this updater to the given updated value. |
| ` final V` | ` https://developer.android.com/reference/java/util/concurrent/atomic/AtomicReferenceFieldUpdater#updateAndGet(T,%20java.util.function.UnaryOperator<V>)(T obj, https://developer.android.com/reference/java/util/function/UnaryOperator<V> updateFunction) ` Atomically updates (with memory effects as specified by `https://developer.android.com/reference/java/lang/invoke/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` | ` https://developer.android.com/reference/java/util/concurrent/atomic/AtomicReferenceFieldUpdater#weakCompareAndSet(T,%20V,%20V)(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. |

| ### Inherited methods |
|---|---|
| From class ` https://developer.android.com/reference/java/lang/Object ` |---|---| | ` https://developer.android.com/reference/java/lang/Object` | ` https://developer.android.com/reference/java/lang/Object#clone()() ` Creates and returns a copy of this object. | | ` boolean` | ` https://developer.android.com/reference/java/lang/Object#equals(java.lang.Object)(https://developer.android.com/reference/java/lang/Object obj) ` Indicates whether some other object is "equal to" this one. | | ` void` | ` https://developer.android.com/reference/java/lang/Object#finalize()() ` Called by the garbage collector on an object when garbage collection determines that there are no more references to the object. | | ` final https://developer.android.com/reference/java/lang/Class<?>` | ` https://developer.android.com/reference/java/lang/Object#getClass()() ` Returns the runtime class of this `Object`. | | ` int` | ` https://developer.android.com/reference/java/lang/Object#hashCode()() ` Returns a hash code value for the object. | | ` final void` | ` https://developer.android.com/reference/java/lang/Object#notify()() ` Wakes up a single thread that is waiting on this object's monitor. | | ` final void` | ` https://developer.android.com/reference/java/lang/Object#notifyAll()() ` Wakes up all threads that are waiting on this object's monitor. | | ` https://developer.android.com/reference/java/lang/String` | ` https://developer.android.com/reference/java/lang/Object#toString()() ` Returns a string representation of the object. | | ` final void` | ` https://developer.android.com/reference/java/lang/Object#wait(long,%20int)(long timeoutMillis, int nanos) ` Causes the current thread to wait until it is awakened, typically by being *notified* or *interrupted*, or until a certain amount of real time has elapsed. | | ` final void` | ` https://developer.android.com/reference/java/lang/Object#wait(long)(long timeoutMillis) ` Causes the current thread to wait until it is awakened, typically by being *notified* or *interrupted*, or until a certain amount of real time has elapsed. | | ` final void` | ` https://developer.android.com/reference/java/lang/Object#wait()() ` Causes the current thread to wait until it is awakened, typically by being *notified* or *interrupted*. | ||

## Protected constructors

### AtomicReferenceFieldUpdater

Added in [API level 1](https://developer.android.com/guide/topics/manifest/uses-sdk-element#ApiLevels)

```
protected AtomicReferenceFieldUpdater ()
```

Protected do-nothing constructor for use by subclasses.

<br />

## Public methods

### accumulateAndGet

Added in [API level 24](https://developer.android.com/guide/topics/manifest/uses-sdk-element#ApiLevels)

```
public final V accumulateAndGet (T obj, 
                V x, 
                BinaryOperator<V> accumulatorFunction)
```

Atomically updates (with memory effects as specified by `https://developer.android.com/reference/java/lang/invoke/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.
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.

<br />

| Parameters ||
|---|---|
| `obj` | `T`: An object whose field to get and set <br /> |
| `x` | `V`: the update value <br /> |
| `accumulatorFunction` | `BinaryOperator`: a side-effect-free function of two arguments <br /> |

| Returns ||
|---|---|
| `V` | the updated value <br /> |

### compareAndSet

Added in [API level 1](https://developer.android.com/guide/topics/manifest/uses-sdk-element#ApiLevels)

```
public 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. 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.

<br />

| Parameters ||
|---|---|
| `obj` | `T`: An object whose field to conditionally set <br /> |
| `expect` | `V`: the expected value <br /> |
| `update` | `V`: the new value <br /> |

| Returns ||
|---|---|
| `boolean` | `true` if successful <br /> |

### get

Added in [API level 1](https://developer.android.com/guide/topics/manifest/uses-sdk-element#ApiLevels)

```
public abstract V get (T obj)
```

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

<br />

| Parameters ||
|---|---|
| `obj` | `T`: An object whose field to get <br /> |

| Returns ||
|---|---|
| `V` | the current value <br /> |

### getAndAccumulate

Added in [API level 24](https://developer.android.com/guide/topics/manifest/uses-sdk-element#ApiLevels)

```
public final V getAndAccumulate (T obj, 
                V x, 
                BinaryOperator<V> accumulatorFunction)
```

Atomically updates (with memory effects as specified by `https://developer.android.com/reference/java/lang/invoke/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.
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.

<br />

| Parameters ||
|---|---|
| `obj` | `T`: An object whose field to get and set <br /> |
| `x` | `V`: the update value <br /> |
| `accumulatorFunction` | `BinaryOperator`: a side-effect-free function of two arguments <br /> |

| Returns ||
|---|---|
| `V` | the previous value <br /> |

### getAndSet

Added in [API level 1](https://developer.android.com/guide/topics/manifest/uses-sdk-element#ApiLevels)

```
public 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.

<br />

| Parameters ||
|---|---|
| `obj` | `T`: An object whose field to get and set <br /> |
| `newValue` | `V`: the new value <br /> |

| Returns ||
|---|---|
| `V` | the previous value <br /> |

### getAndUpdate

Added in [API level 24](https://developer.android.com/guide/topics/manifest/uses-sdk-element#ApiLevels)

```
public final V getAndUpdate (T obj, 
                UnaryOperator<V> updateFunction)
```

Atomically updates (with memory effects as specified by `https://developer.android.com/reference/java/lang/invoke/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. The function should be
side-effect-free, since it may be re-applied when attempted
updates fail due to contention among threads.

<br />

| Parameters ||
|---|---|
| `obj` | `T`: An object whose field to get and set <br /> |
| `updateFunction` | `UnaryOperator`: a side-effect-free function <br /> |

| Returns ||
|---|---|
| `V` | the previous value <br /> |

### lazySet

Added in [API level 9](https://developer.android.com/guide/topics/manifest/uses-sdk-element#ApiLevels)

```
public abstract void lazySet (T obj, 
                V newValue)
```

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

<br />

| Parameters ||
|---|---|
| `obj` | `T`: An object whose field to set <br /> |
| `newValue` | `V`: the new value <br /> |

### newUpdater

Added in [API level 1](https://developer.android.com/guide/topics/manifest/uses-sdk-element#ApiLevels)

```
public static AtomicReferenceFieldUpdater<U, W> newUpdater (Class<U> tclass, 
                Class<W> vclass, 
                String 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.

<br />

| Parameters ||
|---|---|
| `tclass` | `Class`: the class of the objects holding the field <br /> |
| `vclass` | `Class`: the class of the field <br /> |
| `fieldName` | `String`: the name of the field to be updated <br /> |

| Returns ||
|---|---|
| `https://developer.android.com/reference/java/util/concurrent/atomic/AtomicReferenceFieldUpdater<U, W>` | the updater <br /> |

| Throws ||
|---|---|
| `https://developer.android.com/reference/java/lang/ClassCastException` | if the field is of the wrong type |
| `https://developer.android.com/reference/java/lang/IllegalArgumentException` | if the field is not volatile |
| `https://developer.android.com/reference/java/lang/RuntimeException` | 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 |

### set

Added in [API level 1](https://developer.android.com/guide/topics/manifest/uses-sdk-element#ApiLevels)

```
public abstract void set (T obj, 
                V 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`.

<br />

| Parameters ||
|---|---|
| `obj` | `T`: An object whose field to set <br /> |
| `newValue` | `V`: the new value <br /> |

### updateAndGet

Added in [API level 24](https://developer.android.com/guide/topics/manifest/uses-sdk-element#ApiLevels)

```
public final V updateAndGet (T obj, 
                UnaryOperator<V> updateFunction)
```

Atomically updates (with memory effects as specified by `https://developer.android.com/reference/java/lang/invoke/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. The function should be
side-effect-free, since it may be re-applied when attempted
updates fail due to contention among threads.

<br />

| Parameters ||
|---|---|
| `obj` | `T`: An object whose field to get and set <br /> |
| `updateFunction` | `UnaryOperator`: a side-effect-free function <br /> |

| Returns ||
|---|---|
| `V` | the updated value <br /> |

### weakCompareAndSet

Added in [API level 1](https://developer.android.com/guide/topics/manifest/uses-sdk-element#ApiLevels)

```
public 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. 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.

This operation may fail spuriously and does not provide
ordering guarantees, so is only rarely an appropriate
alternative to `compareAndSet`.

<br />

| Parameters ||
|---|---|
| `obj` | `T`: An object whose field to conditionally set <br /> |
| `expect` | `V`: the expected value <br /> |
| `update` | `V`: the new value <br /> |

| Returns ||
|---|---|
| `boolean` | `true` if successful <br /> |