Package org.docx4j.com.google.common.util.concurrent

Class AbstractFuture<V>

java.lang.Object
org.docx4j.com.google.common.util.concurrent.internal.InternalFutureFailureAccess
org.docx4j.com.google.common.util.concurrent.AbstractFuture<V>
All Implemented Interfaces:
Future<V>, ListenableFuture<V>
Direct Known Subclasses:
AbstractFuture.TrustedFuture, GwtFluentFutureCatchingSpecialization
@GwtCompatible(emulated=true) public abstract class AbstractFuture<V> extends InternalFutureFailureAccess implements ListenableFuture<V>
An abstract implementation of ListenableFuture, intended for advanced users only. More common ways to create a ListenableFuture include instantiating a SettableFuture, submitting a task to a ListeningExecutorService, and deriving a Future from an existing one, typically using methods like Futures.transform and Futures.catching.

This class implements all methods in ListenableFuture. Subclasses should provide a way to set the result of the computation through the protected methods set(Object), setFuture(ListenableFuture) and setException(Throwable). Subclasses may also override afterDone(), which will be invoked automatically when the future completes. Subclasses should rarely override other methods.

Since:
1.0

  • Field Details

    • GENERATE_CANCELLATION_CAUSES

      private static final boolean GENERATE_CANCELLATION_CAUSES

    • log

      private static final Logger log

    • SPIN_THRESHOLD_NANOS

      private static final long SPIN_THRESHOLD_NANOS
      See Also:

    • ATOMIC_HELPER

      private static final AbstractFuture.AtomicHelper ATOMIC_HELPER

    • NULL

      private static final Object NULL
      A special value to represent null.

    • value

      private volatile @Nullable Object value
      This field encodes the current state of the future.

      The valid values are:

    • listeners

      private volatile @Nullable AbstractFuture.Listener listeners
      All listeners.

    • waiters

      private volatile @Nullable AbstractFuture.Waiter waiters
      All waiting threads.

  • Constructor Details

    • AbstractFuture

      protected AbstractFuture()
      Constructor for use by subclasses.

  • Method Details

    • removeWaiter

      private void removeWaiter(AbstractFuture.Waiter node)
      Marks the given node as 'deleted' (null waiter) and then scans the list to unlink all deleted nodes. This is an O(n) operation in the common case (and O(n^2) in the worst), but we are saved by two things.
      • This is only called when a waiting thread times out or is interrupted. Both of which should be rare.
      • The waiters list should be very short.

    • get

      @CanIgnoreReturnValue public V get(long timeout, TimeUnit unit) throws InterruptedException, TimeoutException, ExecutionException

      The default AbstractFuture implementation throws InterruptedException if the current thread is interrupted during the call, even if the value is already available.

      Specified by:
      get in interface Future<V>
      Throws:
      CancellationException
      InterruptedException
      TimeoutException
      ExecutionException

    • get

      @CanIgnoreReturnValue public V get() throws InterruptedException, ExecutionException

      The default AbstractFuture implementation throws InterruptedException if the current thread is interrupted during the call, even if the value is already available.

      Specified by:
      get in interface Future<V>
      Throws:
      CancellationException
      InterruptedException
      ExecutionException

    • getDoneValue

      private V getDoneValue(Object obj) throws ExecutionException
      Unboxes obj. Assumes that obj is not null or a AbstractFuture.SetFuture.
      Throws:
      ExecutionException

    • isDone

      public boolean isDone()
      Specified by:
      isDone in interface Future<V>

    • isCancelled

      public boolean isCancelled()
      Specified by:
      isCancelled in interface Future<V>

    • cancel

      @CanIgnoreReturnValue public boolean cancel(boolean mayInterruptIfRunning)

      If a cancellation attempt succeeds on a Future that had previously been set asynchronously, then the cancellation will also be propagated to the delegate Future that was supplied in the setFuture call.

      Rather than override this method to perform additional cancellation work or cleanup, subclasses should override afterDone(), consulting isCancelled() and wasInterrupted() as necessary. This ensures that the work is done even if the future is cancelled without a call to cancel, such as by calling setFuture(cancelledFuture).

      Specified by:
      cancel in interface Future<V>

    • interruptTask

      protected void interruptTask()
      Subclasses can override this method to implement interruption of the future's computation. The method is invoked automatically by a successful call to cancel(true).

      The default implementation does nothing.

      This method is likely to be deprecated. Prefer to override afterDone(), checking wasInterrupted() to decide whether to interrupt your task.

      Since:
      10.0

    • wasInterrupted

      protected final boolean wasInterrupted()
      Returns true if this future was cancelled with mayInterruptIfRunning set to true.
      Since:
      14.0

    • addListener

      public void addListener(Runnable listener, Executor executor)
      Registers a listener to be run on the given executor. The listener will run when the Future's computation is complete or, if the computation is already complete, immediately.

      There is no guaranteed ordering of execution of listeners, but any listener added through this method is guaranteed to be called once the computation is complete.

      Exceptions thrown by a listener will be propagated up to the executor. Any exception thrown during Executor.execute (e.g., a RejectedExecutionException or an exception thrown by direct execution) will be caught and logged.

      Note: For fast, lightweight listeners that would be safe to execute in any thread, consider MoreExecutors.directExecutor(). Otherwise, avoid it. Heavyweight directExecutor listeners can cause problems, and these problems can be difficult to reproduce because they depend on timing. For example:

      • The listener may be executed by the caller of addListener. That caller may be a UI thread or other latency-sensitive thread. This can harm UI responsiveness.
      • The listener may be executed by the thread that completes this Future. That thread may be an internal system thread such as an RPC network thread. Blocking that thread may stall progress of the whole system. It may even cause a deadlock.
      • The listener may delay other listeners, even listeners that are not themselves directExecutor listeners.

      This is the most general listener interface. For common operations performed using listeners, see Futures. For a simplified but general listener interface, see addCallback().

      Memory consistency effects: Actions in a thread prior to adding a listener happen-before its execution begins, perhaps in another thread.

      Guava implementations of ListenableFuture promptly release references to listeners after executing them.

      Specified by:
      addListener in interface ListenableFuture<V>
      Parameters:
      listener - the listener to run when the computation is complete
      executor - the executor to run the listener in
      Since:
      10.0

    • set

      @CanIgnoreReturnValue protected boolean set(@Nullable V value)
      Sets the result of this Future unless this Future has already been cancelled or set (including set asynchronously). When a call to this method returns, the Future is guaranteed to be done only if the call was accepted (in which case it returns true). If it returns false, the Future may have previously been set asynchronously, in which case its result may not be known yet. That result, though not yet known, cannot be overridden by a call to a set* method, only by a call to cancel(boolean).
      Parameters:
      value - the value to be used as the result
      Returns:
      true if the attempt was accepted, completing the Future

    • setException

      @CanIgnoreReturnValue protected boolean setException(Throwable throwable)
      Sets the failed result of this Future unless this Future has already been cancelled or set (including set asynchronously). When a call to this method returns, the Future is guaranteed to be done only if the call was accepted (in which case it returns true). If it returns false, the Future may have previously been set asynchronously, in which case its result may not be known yet. That result, though not yet known, cannot be overridden by a call to a set* method, only by a call to cancel(boolean).
      Parameters:
      throwable - the exception to be used as the failed result
      Returns:
      true if the attempt was accepted, completing the Future

    • setFuture

      @Beta @CanIgnoreReturnValue protected boolean setFuture(ListenableFuture<? extends V> future)
      Sets the result of this Future to match the supplied input Future once the supplied Future is done, unless this Future has already been cancelled or set (including "set asynchronously," defined below).

      If the supplied future is done when this method is called and the call is accepted, then this future is guaranteed to have been completed with the supplied future by the time this method returns. If the supplied future is not done and the call is accepted, then the future will be set asynchronously. Note that such a result, though not yet known, cannot be overridden by a call to a set* method, only by a call to cancel(boolean).

      If the call setFuture(delegate) is accepted and this Future is later cancelled, cancellation will be propagated to delegate. Additionally, any call to setFuture after any cancellation will propagate cancellation to the supplied Future.

      Note that, even if the supplied future is cancelled and it causes this future to complete, it will never trigger interruption behavior. In particular, it will not cause this future to invoke the interruptTask() method, and the wasInterrupted() method will not return true.

      Parameters:
      future - the future to delegate to
      Returns:
      true if the attempt was accepted, indicating that the Future was not previously cancelled or set.
      Since:
      19.0

    • getFutureValue

      private static Object getFutureValue(ListenableFuture<?> future)
      Returns a value that satisfies the contract of the value field based on the state of given future.

      This is approximately the inverse of getDoneValue(Object)

    • getUninterruptibly

      private static <V> V getUninterruptibly(Future<V> future) throws ExecutionException
      An inlined private copy of Uninterruptibles.getUninterruptibly(java.util.concurrent.Future<V>) used to break an internal dependency on other /util/concurrent classes.
      Throws:
      ExecutionException

    • complete

      private static void complete(AbstractFuture<?> future)
      Unblocks all threads and runs all listeners.

    • afterDone

      @Beta @ForOverride protected void afterDone()
      Callback method that is called exactly once after the future is completed.

      If interruptTask() is also run during completion, afterDone() runs after it.

      The default implementation of this method in AbstractFuture does nothing. This is intended for very lightweight cleanup work, for example, timing statistics or clearing fields. If your task does anything heavier consider, just using a listener with an executor.

      Since:
      20.0

    • tryInternalFastPathGetFailure

      protected final @Nullable Throwable tryInternalFastPathGetFailure()
      Usually returns null but, if this Future has failed, may optionally return the cause of the failure. "Failure" means specifically "completed with an exception"; it does not include "was cancelled." To be explicit: If this method returns a non-null value, then:
      • isDone() must return true
      • isCancelled() must return false
      • get() must not block, and it must throw an ExecutionException with the return value of this method as its cause

      This method is protected so that classes like org.docx4j.com.google.common.util.concurrent.SettableFuture do not expose it to their users as an instance method. In the unlikely event that you need to call this method, call InternalFutures.tryInternalFastPathGetFailure(InternalFutureFailureAccess).

      Specified by:
      tryInternalFastPathGetFailure in class InternalFutureFailureAccess
      Since:
      27.0

    • maybePropagateCancellationTo

      final void maybePropagateCancellationTo(@Nullable Future<?> related)
      If this future has been cancelled (and possibly interrupted), cancels (and possibly interrupts) the given future (if available).

    • releaseWaiters

      private void releaseWaiters()
      Releases all threads in the waiters list, and clears the list.

    • clearListeners

      private AbstractFuture.Listener clearListeners(AbstractFuture.Listener onto)
      Clears the listeners list and prepends its contents to onto, least recently added first.

    • toString

      public String toString()
      Overrides:
      toString in class Object

    • pendingToString

      protected @Nullable String pendingToString()
      Provide a human-readable explanation of why this future has not yet completed.
      Returns:
      null if an explanation cannot be provided because the future is done.
      Since:
      23.0

    • addDoneString

      private void addDoneString(StringBuilder builder)

    • userObjectToString

      private String userObjectToString(Object o)
      Helper for printing user supplied objects into our toString method.

    • executeListener

      private static void executeListener(Runnable runnable, Executor executor)
      Submits the given runnable to the given Executor catching and logging all runtime exceptions thrown by the executor.

    • cancellationExceptionWithCause

      private static CancellationException cancellationExceptionWithCause(@Nullable String message, @Nullable Throwable cause)