4.  Serialized forms of ALL objects are subject to change unless noted
    otherwise. Do not persist these and assume they can be read by a future
    version of the library.

5.  Our classes are not designed to protect against a malicious caller. You
    should not use them for communication between trusted and untrusted code.

6.  For the mainline flavor, we test the libraries using OpenJDK 8, 11, and 17

   * or the least double greater than or equal to the precise value of x.
   */
  abstract double roundToDoubleArbitrarily(X x);

  /** Returns the sign of x: either -1, 0, or 1. */
  abstract int sign(X x);

  /** Returns d's value as an X, rounded with the specified mode. */
  abstract X toX(double d, RoundingMode mode);

  /** Returns a - b, guaranteed that both arguments are nonnegative. */

   * {@link Collection#contains(Object)} (which does not generally throw if the object cannot be
   * present in the collection), and the desire to have this method's behavior be compatible with
   * {@code edges().contains(endpoints)}.
   *
   * @since 27.1
   */
  boolean hasEdgeConnecting(EndpointPair<N> endpoints);

 *
 * <p>Listeners are registered once via {@link #addListener} and then may be invoked by {@linkplain
 * #enqueue enqueueing} and then {@linkplain #dispatch dispatching} events.
 *
 * <p>The API of this class is designed to make it easy to achieve the following properties
 *
 * <ul>
 *   <li>Multiple events for the same listener are never dispatched concurrently.
 *   <li>Events for the different listeners are dispatched concurrently.