*
     * @throws IllegalStateException if an id has already been loaded.
     */
    public long createId() {
        long newId = sequence.updateAndGet(it -> it == USED_ASSIGNED_ID_MARKER ? it : it + 1);
        if (newId == USED_ASSIGNED_ID_MARKER) {
            throw new IllegalStateException("Cannot create a new id after one has been loaded");
        }

        }
      }
    }
  }

  /** updateAndGet adds given value to current, and returns current value */
  public void testUpdateAndGetWithSum() {
    AtomicDoubleArray aa = new AtomicDoubleArray(SIZE);
    for (int i : new int[] {0, SIZE - 1}) {
      for (double x : VALUES) {
        for (double y : VALUES) {
          aa.set(i, x);
          double z = aa.updateAndGet(i, value -> value + y);

   * returns the new value. If there is not currently a value associated with {@code key}, the
   * function is applied to {@code 0L}.
   *
   * @since 21.0
   */
  @CanIgnoreReturnValue
  public long updateAndGet(K key, LongUnaryOperator updaterFunction) {
    checkNotNull(updaterFunction);
    Long result =
        map.compute(
            key,