Module java.base
Package java.util.concurrent.atomic

Class AtomicReference<V>

java.lang.Object
java.util.concurrent.atomic.AtomicReference<V>
Type Parameters:
V - The type of object referred to by this reference
All Implemented Interfaces:
Serializable
public class AtomicReference<V> extends Object implements Serializable
An object reference that may be updated atomically. See the VarHandle specification for descriptions of the properties of atomic accesses.
Since:
1.5
See Also:
Serialized Form

  • Constructor Details

    • AtomicReference

      public AtomicReference​(V initialValue)
      Creates a new AtomicReference with the given initial value.
      Parameters:
      initialValue - the initial value

    • AtomicReference

      public AtomicReference()
      Creates a new AtomicReference with null initial value.

  • Method Details

    • get

      public final V get()
      Returns the current value, with memory effects as specified by VarHandle.getVolatile(java.lang.Object...).
      Returns:
      the current value

    • set

      public final void set​(V newValue)
      Sets the value to newValue, with memory effects as specified by VarHandle.setVolatile(java.lang.Object...).
      Parameters:
      newValue - the new value

    • lazySet

      public final void lazySet​(V newValue)
      Sets the value to newValue, with memory effects as specified by VarHandle.setRelease(java.lang.Object...).
      Parameters:
      newValue - the new value
      Since:
      1.6

    • compareAndSet

      public final boolean compareAndSet​(V expectedValue, V newValue)
      Atomically sets the value to newValue if the current value == expectedValue, with memory effects as specified by VarHandle.compareAndSet(java.lang.Object...).
      Parameters:
      expectedValue - the expected value
      newValue - the new value
      Returns:
      true if successful. False return indicates that the actual value was not equal to the expected value.

    • weakCompareAndSet

      @Deprecated(since="9") public final boolean weakCompareAndSet​(V expectedValue, V newValue)
      Deprecated.
      This method has plain memory effects but the method name implies volatile memory effects (see methods such as compareAndExchange(V, V) and compareAndSet(V, V)). To avoid confusion over plain or volatile memory effects it is recommended that the method weakCompareAndSetPlain(V, V) be used instead.
      Possibly atomically sets the value to newValue if the current value == expectedValue, with memory effects as specified by VarHandle.weakCompareAndSetPlain(java.lang.Object...).
      Parameters:
      expectedValue - the expected value
      newValue - the new value
      Returns:
      true if successful
      See Also:
      weakCompareAndSetPlain(V, V)

    • weakCompareAndSetPlain

      public final boolean weakCompareAndSetPlain​(V expectedValue, V newValue)
      Possibly atomically sets the value to newValue if the current value == expectedValue, with memory effects as specified by VarHandle.weakCompareAndSetPlain(java.lang.Object...).
      Parameters:
      expectedValue - the expected value
      newValue - the new value
      Returns:
      true if successful
      Since:
      9

    • getAndSet

      public final V getAndSet​(V newValue)
      Atomically sets the value to newValue and returns the old value, with memory effects as specified by VarHandle.getAndSet(java.lang.Object...).
      Parameters:
      newValue - the new value
      Returns:
      the previous value

    • getAndUpdate

      public final V getAndUpdate​(UnaryOperator<V> updateFunction)
      Atomically updates (with memory effects as specified by VarHandle.compareAndSet(java.lang.Object...)) the current value 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:
      updateFunction - a side-effect-free function
      Returns:
      the previous value
      Since:
      1.8

    • updateAndGet

      public final V updateAndGet​(UnaryOperator<V> updateFunction)
      Atomically updates (with memory effects as specified by VarHandle.compareAndSet(java.lang.Object...)) the current value 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:
      updateFunction - a side-effect-free function
      Returns:
      the updated value
      Since:
      1.8

    • getAndAccumulate

      public final V getAndAccumulate​(V x, BinaryOperator<V> accumulatorFunction)
      Atomically updates (with memory effects as specified by VarHandle.compareAndSet(java.lang.Object...)) the current value 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:
      x - the update value
      accumulatorFunction - a side-effect-free function of two arguments
      Returns:
      the previous value
      Since:
      1.8

    • accumulateAndGet

      public final V accumulateAndGet​(V x, BinaryOperator<V> accumulatorFunction)
      Atomically updates (with memory effects as specified by VarHandle.compareAndSet(java.lang.Object...)) the current value 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:
      x - the update value
      accumulatorFunction - a side-effect-free function of two arguments
      Returns:
      the updated value
      Since:
      1.8

    • toString

      public String toString()
      Returns the String representation of the current value.
      Overrides:
      toString in class Object
      Returns:
      the String representation of the current value

    • getPlain

      public final V getPlain()
      Returns the current value, with memory semantics of reading as if the variable was declared non-volatile.
      Returns:
      the value
      Since:
      9

    • setPlain

      public final void setPlain​(V newValue)
      Sets the value to newValue, with memory semantics of setting as if the variable was declared non-volatile and non-final.
      Parameters:
      newValue - the new value
      Since:
      9

    • getOpaque

      public final V getOpaque()
      Returns the current value, with memory effects as specified by VarHandle.getOpaque(java.lang.Object...).
      Returns:
      the value
      Since:
      9

    • setOpaque

      public final void setOpaque​(V newValue)
      Sets the value to newValue, with memory effects as specified by VarHandle.setOpaque(java.lang.Object...).
      Parameters:
      newValue - the new value
      Since:
      9

    • getAcquire

      public final V getAcquire()
      Returns the current value, with memory effects as specified by VarHandle.getAcquire(java.lang.Object...).
      Returns:
      the value
      Since:
      9

    • setRelease

      public final void setRelease​(V newValue)
      Sets the value to newValue, with memory effects as specified by VarHandle.setRelease(java.lang.Object...).
      Parameters:
      newValue - the new value
      Since:
      9

    • compareAndExchange

      public final V compareAndExchange​(V expectedValue, V newValue)
      Atomically sets the value to newValue if the current value, referred to as the witness value, == expectedValue, with memory effects as specified by VarHandle.compareAndExchange(java.lang.Object...).
      Parameters:
      expectedValue - the expected value
      newValue - the new value
      Returns:
      the witness value, which will be the same as the expected value if successful
      Since:
      9

    • compareAndExchangeAcquire

      public final V compareAndExchangeAcquire​(V expectedValue, V newValue)
      Atomically sets the value to newValue if the current value, referred to as the witness value, == expectedValue, with memory effects as specified by VarHandle.compareAndExchangeAcquire(java.lang.Object...).
      Parameters:
      expectedValue - the expected value
      newValue - the new value
      Returns:
      the witness value, which will be the same as the expected value if successful
      Since:
      9

    • compareAndExchangeRelease

      public final V compareAndExchangeRelease​(V expectedValue, V newValue)
      Atomically sets the value to newValue if the current value, referred to as the witness value, == expectedValue, with memory effects as specified by VarHandle.compareAndExchangeRelease(java.lang.Object...).
      Parameters:
      expectedValue - the expected value
      newValue - the new value
      Returns:
      the witness value, which will be the same as the expected value if successful
      Since:
      9

    • weakCompareAndSetVolatile

      public final boolean weakCompareAndSetVolatile​(V expectedValue, V newValue)
      Possibly atomically sets the value to newValue if the current value == expectedValue, with memory effects as specified by VarHandle.weakCompareAndSet(java.lang.Object...).
      Parameters:
      expectedValue - the expected value
      newValue - the new value
      Returns:
      true if successful
      Since:
      9

    • weakCompareAndSetAcquire

      public final boolean weakCompareAndSetAcquire​(V expectedValue, V newValue)
      Possibly atomically sets the value to newValue if the current value == expectedValue, with memory effects as specified by VarHandle.weakCompareAndSetAcquire(java.lang.Object...).
      Parameters:
      expectedValue - the expected value
      newValue - the new value
      Returns:
      true if successful
      Since:
      9

    • weakCompareAndSetRelease

      public final boolean weakCompareAndSetRelease​(V expectedValue, V newValue)
      Possibly atomically sets the value to newValue if the current value == expectedValue, with memory effects as specified by VarHandle.weakCompareAndSetRelease(java.lang.Object...).
      Parameters:
      expectedValue - the expected value
      newValue - the new value
      Returns:
      true if successful
      Since:
      9