long oldValue = atomic.get();
      if (oldValue == 0L || atomic.compareAndSet(oldValue, 0L)) {
        // only remove after setting to zero, to avoid concurrent updates
        map.remove(key, atomic);
        // succeed even if the remove fails, since the value was already adjusted
        return oldValue;
      }
    }
  }

  /**
   * If {@code (key, value)} is currently in the map, this method removes it and returns true;

    Builder<String, Integer> builder =
        ImmutableSortedMap.<String, Integer>naturalOrder()
            .put("one", 1)
            .put("one", 2); // throwing on this line would be even better

    try {
      builder.build();
      fail();
    } catch (IllegalArgumentException expected) {
    }
  }

  public void testOf() {

   * safe to do so. The exact circumstances under which a copy will or will not be performed are
   * undocumented and subject to change.
   *
   * <p>This method is safe to use even when {@code sortedMultiset} is a synchronized or concurrent
   * collection that is currently being modified by another thread.
   *
   * @throws NullPointerException if {@code sortedMultiset} or any of its elements is null

      return valueOrNull != null;
    }

    @Override
    public @NonNull T next() {
      T result = valueOrNull;
      valueOrNull = null;
      // We put the common case first, even though it's unlikely to matter if the code is run much:
      // https://shipilev.net/jvm/anatomy-quarks/28-frequency-based-code-layout/
      if (result != null) {
        return result;
      }