Method cancel

output/java_guava/1.4.17/AbstractFuture.java:533–567

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

(boolean mayInterruptIfRunning)

   */

  @CanIgnoreReturnValue
  @Override
  public boolean cancel(boolean mayInterruptIfRunning) {
    Object localValue = value;
    if (localValue == null | localValue instanceof AbstractFuture.SetFuture) {
      // Try to delay allocating the exception. At this point we may still lose the CAS, but it is
      // certainly less likely.
      Throwable cause =
        GENERATE_CANCELLATION_CAUSES
          ? new CancellationException("Future.cancel() was called.")
          : null;
      Object valueToSet = new Cancellation(mayInterruptIfRunning, cause);
      do {
        if (ATOMIC_HELPER.casValue(this, localValue, valueToSet)) {
          // We call interuptTask before calling complete(), which is consistent with
          // FutureTask
          if (mayInterruptIfRunning) {
            interruptTask();
          }
          complete();
          if (localValue instanceof AbstractFuture.SetFuture) {
            // propagate cancellation to the future set in setfuture, this is racy, and we don't
            // care if we are successful or not.
            ((AbstractFuture<?>.SetFuture) localValue).future.cancel(mayInterruptIfRunning);
          }
          return true;
        }
        // obj changed, reread
        localValue = value;
        // obj cannot be null at this point, because value can only change from null to non-null. So
        // if value changed (and it did since we lost the CAS), then it cannot be null.
      } while (localValue instanceof AbstractFuture.SetFuture);
    }
    return false;
  }

  /**
   * Subclasses can override this method to implement interruption of the future's computation. The