# Class AtomicLongFieldUpdater<T>

java.lang.Object
java.util.concurrent.atomic.AtomicLongFieldUpdater<T>

Type Parameters:
  `T` - The type of the object holding the updatable field

public abstract class AtomicLongFieldUpdater<T> extends Object
A reflection-based utility that enables atomic updates to designated `volatile long` 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.

Object arguments for parameters of type `T` that are not instances of the class passed to `newUpdater(java.lang.Class<U>, java.lang.String)` will result in a `ClassCastException` being thrown.

Since:
  1.5

- ## Constructor Summary

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

- ## Method Summary

  Modifier and Type
  Method
  Description
  `final long`
  `accumulateAndGet(T obj, long x, LongBinaryOperator 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.
  `long`
  `addAndGet(T obj, long 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, long expect, long 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.
  `long`
  `decrementAndGet(T obj)`
  Atomically decrements by one the current value of the field of the given object managed by this updater.
  `abstract long`
  `get(T obj)`
  Returns the current value held in the field of the given object managed by this updater.
  `final long`
  `getAndAccumulate(T obj, long x, LongBinaryOperator 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.
  `long`
  `getAndAdd(T obj, long delta)`
  Atomically adds the given value to the current value of the field of the given object managed by this updater.
  `long`
  `getAndDecrement(T obj)`
  Atomically decrements by one the current value of the field of the given object managed by this updater.
  `long`
  `getAndIncrement(T obj)`
  Atomically increments by one the current value of the field of the given object managed by this updater.
  `long`
  `getAndSet(T obj, long newValue)`
  Atomically sets the field of the given object managed by this updater to the given value and returns the old value.
  `final long`
  `getAndUpdate(T obj, LongUnaryOperator 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.
  `long`
  `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, long newValue)`
  Eventually sets the field of the given object managed by this updater to the given updated value.
  `static <U> AtomicLongFieldUpdater<U>`
  `newUpdater(Class<U> tclass, String fieldName)`
  Creates and returns an updater for objects with the given field.
  `abstract void`
  `set(T obj, long newValue)`
  Sets the field of the given object managed by this updater to the given updated value.
  `final long`
  `updateAndGet(T obj, LongUnaryOperator 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, long expect, long 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 declared in class java.lang.Object

  `clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait`

- ## Constructor Details

  - ### AtomicLongFieldUpdater

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

- ## Method Details

  - ### newUpdater

    public static <U> AtomicLongFieldUpdater<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.
    Type Parameters:
      `U` - the type of instances of tclass
    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 long type
      `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

  - ### compareAndSet

    public abstract boolean compareAndSet(T obj, long expect, long 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 obj, long expect, long 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`.

    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 obj, long 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, long 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 long get(T 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 long getAndSet(T obj, long 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 long 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 long 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 long getAndAdd(T obj, long 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 long 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 long 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 long addAndGet(T obj, long 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

  - ### getAndUpdate

    public final long getAndUpdate(T obj, LongUnaryOperator 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. 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 long updateAndGet(T obj, LongUnaryOperator 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. 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 long getAndAccumulate(T obj, long x, LongBinaryOperator 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. 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 long accumulateAndGet(T obj, long x, LongBinaryOperator 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. 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