* provide much stronger guarantees.
 *
 * <h3>Comparison to a map of collections</h3>
 *
 * <p>Multimaps are commonly used in places where a {@code Map<K, Collection<V>>} would otherwise
 * have appeared. The differences include:
 *
 * <ul>
 *   <li>There is no need to populate an empty collection before adding an entry with {@link #put
 *       put}.
 *   <li>{@code get} never returns {@code null}, only an empty collection.

 * class was added for Java 8. The two classes are extremely similar, but incompatible (they cannot
 * share a common supertype). <i>All</i> known differences are listed either here or with the
 * relevant methods below.
 *
 * <ul>
 *   <li>This class is serializable; {@code java.util.Optional} is not.

 * may also refer to servers and workgroups. If the resource is a file or
 * directory the methods of <code>SmbFile</code> follow the behavior of
 * the well known {@link java.io.File} class. One fundamental difference
 * is the usage of a URL scheme [1] to specify the target file or
 * directory. SmbFile URLs have the following syntax:
 *
 * <blockquote>
 * 
 * <pre>

    assertThat(graph).isNotEqualTo(g2);
  }

  // Node/edge sets and node/edge connections are the same, but graph properties differ.
  // In this case the graphs are considered equivalent; the property differences are irrelevant.
  @Test
  public void equivalent_propertiesDiffer() {
    graph.putEdge(N1, N2);

    MutableGraph<Integer> g2 =
        GraphBuilder.from(graph).allowsSelfLoops(!graph.allowsSelfLoops()).build();

  @Override
  public int hashCode() {
    return Sets.hashCodeImpl(this);
  }

  // This declaration is needed to make Set.iterator() and
  // ImmutableCollection.iterator() appear consistent to javac's type inference.
  @Override
  public abstract UnmodifiableIterator<E> iterator();

  abstract static class CachingAsList<E> extends ImmutableSet<E> {
    @LazyInit private transient ImmutableList<E> asList;

    @Override

 * Verify.verify(bill.status() == Status.UNPAID,
 *     "Unexpected bill status: %s", bill.status());
 * }</pre>
 *
 * <h3>Comparison to alternatives</h3>
 *
 * <p><b>Note:</b> In some cases the differences explained below can be subtle. When it's unclear
 * which approach to use, <b>don't worry</b> too much about it; just pick something that seems
 * reasonable and it will be fine.
 *
 * <ul>

 * class was added for Java 8. The two classes are extremely similar, but incompatible (they cannot
 * share a common supertype). <i>All</i> known differences are listed either here or with the
 * relevant methods below.
 *
 * <ul>
 *   <li>This class is serializable; {@code java.util.Optional} is not.

 * Iterables} class.
 *
 * <p><a id="streams"></a>
 *
 * <h3>Comparison to streams</h3>
 *
 * <p>{@link Stream} is similar to this class, but generally more powerful, and certainly more
 * standard. Key differences include:
 *
 * <ul>
 *   <li>A stream is <i>single-use</i>; it becomes invalid as soon as any "terminal operation" such
 *       as {@code findFirst()} or {@code iterator()} is invoked. (Even though {@code Stream}

    // We define the arithmetic means X_n = 1/n \sum_{i=1}^n x_i, and Y_n = 1/n \sum_{i=1}^n y_i.
    // We also define the sum of the products of the differences from the means
    //           C_n = \sum_{i=1}^n x_i y_i - n X_n Y_n
    // for all n >= 1. Then for all n > 1:
    //       C_{n-1} = \sum_{i=1}^{n-1} x_i y_i - (n-1) X_{n-1} Y_{n-1}

 *
 * <p>Starting with Java 8, the core Java class libraries provide a new "Streams" library (in {@code
 * java.util.stream}), which is similar to {@code FluentIterable} but generally more powerful. Key
 * differences include:
 *
 * <ul>
 *   <li>A stream is <i>single-use</i>; it becomes invalid as soon as any "terminal operation" such
 *       as {@code findFirst()} or {@code iterator()} is invoked. (Even though {@code Stream}