try {
      insert(e);
    } finally {
      monitor.leave();
    }
  }

  @CanIgnoreReturnValue
  @Override
  public @Nullable E poll() {
    Monitor monitor = this.monitor;
    if (monitor.enterIf(notEmpty)) {
      try {
        return extract();
      } finally {
        monitor.leave();
      }
    } else {
      return null;
    }
  }

      } finally {
        monitor.leave();
      }
    } else {
      return null;
    }
  }

  @CanIgnoreReturnValue // pushed down from class to method
  @Override
  public E take() throws InterruptedException {
    Monitor monitor = this.monitor;
    monitor.enterWhen(notEmpty);
    try {
      return q.poll();
    } finally {
      monitor.leave();
    }
  }

        notifyFailed(shutdownFailure);
      } finally {
        monitor.leave();
        dispatchListenerEvents();
      }
    }
    return this;
  }

  @Override
  public final void awaitRunning() {
    monitor.enterWhenUninterruptibly(hasReachedRunning);
    try {
      checkCurrentState(RUNNING);
    } finally {
      monitor.leave();
    }
  }

  /**
   * @since 28.0
   */

        notifyFailed(shutdownFailure);
      } finally {
        monitor.leave();
        dispatchListenerEvents();
      }
    }
    return this;
  }

  @Override
  public final void awaitRunning() {
    monitor.enterWhenUninterruptibly(hasReachedRunning);
    try {
      checkCurrentState(RUNNING);
    } finally {
      monitor.leave();
    }
  }

  @Override

   *
   * @throws UnsupportedOperationException always
   * @deprecated Unsupported operation.
   */
  @Deprecated
  @Override
  @DoNotCall("Always throws UnsupportedOperationException")
  public final void remove(Range<K> range) {
    throw new UnsupportedOperationException();
  }

  /**
   * Guaranteed to throw an exception and leave the {@code RangeMap} unmodified.

  int internalArrayEnd() {
    throw new UnsupportedOperationException();
  }

  @Override
  public abstract boolean contains(@Nullable Object object);

  /**
   * Guaranteed to throw an exception and leave the collection unmodified.
   *
   * @throws UnsupportedOperationException always
   * @deprecated Unsupported operation.
   */
  @CanIgnoreReturnValue
  @Deprecated
  @Override

    Range<K> lastRange = ranges.get(ranges.size() - 1);
    return Range.create(firstRange.lowerBound, lastRange.upperBound);
  }

  /**
   * Guaranteed to throw an exception and leave the {@code RangeMap} unmodified.
   *
   * @throws UnsupportedOperationException always
   * @deprecated Unsupported operation.
   */
  @Deprecated
  @Override

        }
      } finally {
        monitor.leave();
      }
    }

    void addListener(Listener listener, Executor executor) {
      listeners.addListener(listener, executor);
    }

    void awaitHealthy() {
      monitor.enterWhenUninterruptibly(awaitHealthGuard);
      try {
        checkHealthy();
      } finally {
        monitor.leave();
      }
    }

  //
  // 2. Since you can enter the monitor without a guard at all, some
  //    places you'll have monitor.enter()/monitor.leave() and other
  //    places you'll have guard.enter()/guard.leave() even though
  //    it's the same lock being acquired underneath. Always using
  //    monitor.enterXXX()/monitor.leave() will make it really clear
  //    which lock is held at any point in the code.
  //

    } else {
      assertNull(task.get(UNEXPECTED_HANG_DELAY_MILLIS, TimeUnit.MILLISECONDS));
    }
  }

  @Override
  protected void tearDown() throws Exception {
    // We don't want to leave stray threads running after each test. At this point, every thread
    // launched by this test is either:
    //
    // (a) Blocked attempting to enter the monitor.
    // (b) Waiting for the single guard to become satisfied.