* started nor stopped.
     */
    FAILED,
  }

  /**
   * A listener for the various state changes that a {@link Service} goes through in its lifecycle.
   *
   * <p>All methods are no-ops by default, implementors should override the ones they care about.
   *
   * @author Luke Sandberg
   * @since 15.0 (present as an interface in 13.0)
   */
  abstract class Listener {
    /**

      fail("a call to multiset.setCount() to decrease an element's count should throw");
    } catch (UnsupportedOperationException expected) {
    }
  }

  // Unconditional setCount no-ops.

  private void assertZeroToZero() {
    assertSetCount(e3(), 0);
  }

  private void assertOneToOne() {
    assertSetCount(e0(), 1);
  }

  private void assertThreeToThree() {

     * started nor stopped.
     */
    FAILED,
  }

  /**
   * A listener for the various state changes that a {@link Service} goes through in its lifecycle.
   *
   * <p>All methods are no-ops by default, implementors should override the ones they care about.
   *
   * @author Luke Sandberg
   * @since 15.0 (present as an interface in 13.0)
   */
  abstract class Listener {
    /**

      fail("a call to multiset.setCount() to decrease an element's count should throw");
    } catch (UnsupportedOperationException expected) {
    }
  }

  // Unconditional setCount no-ops.

  private void assertZeroToZero() {
    assertSetCount(e3(), 0);
  }

  private void assertOneToOne() {
    assertSetCount(e0(), 1);
  }

  private void assertThreeToThree() {

      // otherwise have another task queued on to it. Note the exception to this, cancellation, is
      // specially handled in execute() - execute() calls triggered by cancellation are no-ops, and
      // thus don't count.
      requireNonNull(sequencer).latestTaskQueue = executingTaskQueue;
      sequencer = null;
      try {
        // requireNonNull is safe, as discussed above.

      // otherwise have another task queued on to it. Note the exception to this, cancellation, is
      // specially handled in execute() - execute() calls triggered by cancellation are no-ops, and
      // thus don't count.
      requireNonNull(sequencer).latestTaskQueue = executingTaskQueue;
      sequencer = null;
      try {
        // requireNonNull is safe, as discussed above.