checkState((type == Type.SORTED) == (comparator != null));
  }

  /** Returns an instance which specifies that no ordering is guaranteed. */
  public static <S> ElementOrder<S> unordered() {
    return new ElementOrder<>(Type.UNORDERED, null);
  }

  /**
   * Returns an instance which specifies that ordering is guaranteed to be always be the same across

  /**
   * Specifies the order of iteration for the elements of {@link Network#nodes()}.
   *
   * <p>The default value is {@link ElementOrder#insertion() insertion order}.
   */
  public <N1 extends N> NetworkBuilder<N1, E> nodeOrder(ElementOrder<N1> nodeOrder) {
    NetworkBuilder<N1, E> newBuilder = cast();
    newBuilder.nodeOrder = checkNotNull(nodeOrder);
    return newBuilder;
  }

  /**

  public <N1 extends N, V1 extends V> ImmutableValueGraph.Builder<N1, V1> immutable() {
    ValueGraphBuilder<N1, V1> castBuilder = cast();
    return new ImmutableValueGraph.Builder<>(castBuilder);
  }

  /**
   * Specifies whether the graph will allow self-loops (edges that connect a node to itself).
   * Attempting to add a self-loop to a graph that does not allow them will throw an {@link
   * UnsupportedOperationException}.
   *

  }

  /**
   * Specifies the expected number of nodes in the graph.
   *
   * @throws IllegalArgumentException if {@code expectedNodeCount} is negative
   */
  @CanIgnoreReturnValue
  public GraphBuilder<N> expectedNodeCount(int expectedNodeCount) {
    this.expectedNodeCount = checkNonNegative(expectedNodeCount);
    return this;
  }

  /**

    checkArgument(maximumSize >= 0, "maximum size must not be negative");
    this.maximumSize = maximumSize;
    return this;
  }

  /**
   * Specifies the maximum weight of entries the cache may contain. Weight is determined using the
   * {@link Weigher} specified with {@link #weigher}, and use of this method requires a
   * corresponding call to {@link #weigher} prior to calling {@link #build}.
   *

    checkArgument(maximumSize >= 0, "maximum size must not be negative");
    this.maximumSize = maximumSize;
    return this;
  }

  /**
   * Specifies the maximum weight of entries the cache may contain. Weight is determined using the
   * {@link Weigher} specified with {@link #weigher}, and use of this method requires a
   * corresponding call to {@link #weigher} prior to calling {@link #build}.
   *

   */
  @Deprecated
  public Quantiles() {}

  /** Specifies the computation of a median (i.e. the 1st 2-quantile). */
  public static ScaleAndIndex median() {
    return scale(2).index(1);
  }

  /** Specifies the computation of quartiles (i.e. 4-quantiles). */
  public static Scale quartiles() {
    return scale(4);
  }

  /** Specifies the computation of percentiles (i.e. 100-quantiles). */

    }
  }

  public void testNoNullValues() {
    for (StandardSystemProperty property : StandardSystemProperty.values()) {
      // Even though the contract in System.getProperties() specifies that a value will exist for
      // all of the listed keys, for some reason the "java.compiler" key returns null in some JVMs.
      if (property == JAVA_COMPILER) {
        continue;
      }
      // Removed in Java 9:

    }
  }

  public void testNoNullValues() {
    for (StandardSystemProperty property : StandardSystemProperty.values()) {
      // Even though the contract in System.getProperties() specifies that a value will exist for
      // all of the listed keys, for some reason the "java.compiler" key returns null in some JVMs.
      if (property == JAVA_COMPILER) {
        continue;
      }
      // Removed in Java 9:

 * Iterator#remove} operations. This utility takes the brute-force approach of trying <i>all</i>
 * possible sequences of these operations, up to a given number of steps. So, if the caller
 * specifies to use <i>n</i> steps, a total of <i>3^n</i> tests are actually performed.
 *
 * <p>For instance, if <i>steps</i> is 5, one example sequence that will be tested is:
 *
 * <ol>
 *   <li>remove();
 *   <li>hasNext()