// Graph query methods

  /**
   * Returns true if {@code graph} has at least one cycle. A cycle is defined as a non-empty subset
   * of edges in a graph arranged to form a path (a sequence of adjacent outgoing edges) starting
   * and ending with the same node.
   *
   * <p>This method will detect any non-empty cycle, including self-loops (a cycle of length 1).
   */
  public static <N> boolean hasCycle(Graph<N> graph) {

    // always point to "a".
    assertEquals("a", cycle.iterator().next());
  }

  public void testCycle_emptyIterable() {
    FluentIterable<Integer> cycle = FluentIterable.<Integer>of().cycle();
    assertFalse(cycle.iterator().hasNext());
  }

  public void testCycle_removingAllElementsStopsCycle() {
    FluentIterable<Integer> cycle = fluent(1, 2).cycle();
    Iterator<Integer> iterator = cycle.iterator();

  }

  public void testConcat_infiniteIterable() throws IOException {
    CharSource source = CharSource.wrap("abcd");
    Iterable<CharSource> cycle = Iterables.cycle(ImmutableList.of(source));
    CharSource concatenated = CharSource.concat(cycle);

    String expected = "abcdabcd";

    // read the first 8 chars manually, since there's no equivalent to ByteSource.slice

      <version>4.13.2</version>
    </dependency>
    <dependency>
      <!--
      Do not include Truth in non-test scope! Doing so creates a problematic dependency cycle.
      -->
      <groupId>com.google.truth</groupId>
      <artifactId>truth</artifactId>
      <version>${truth.version}</version>
      <scope>test</scope>
      <exclusions>
        <exclusion>

   * should use an explicit {@code break} or be certain that you will eventually remove all the
   * elements.
   */
  @SafeVarargs
  public static <T extends @Nullable Object> Iterator<T> cycle(T... elements) {
    return cycle(Lists.newArrayList(elements));
  }

  /**
   * Returns an Iterator that walks the specified array, nulling out elements behind it. This can

   * use {@code Stream.generate(() -> collection).flatMap(Collection::stream)}.
   */
  public final FluentIterable<E> cycle() {
    return from(Iterables.cycle(getDelegate()));
  }

  /**
   * Returns a fluent iterable whose iterators traverse first the elements of this fluent iterable,

   *
   * This means that dynamically loaded web applications and OSGi bundles can't be unloaded.
   *
   * If the library is loaded in an application class loader, we try to break the cycle by loading
   * Finalizer in its own independent class loader:
   *
   * System class loader -> Application class loader -> ReferenceMap -> FinalizableReferenceQueue ->
   * etc. -> Decoupled class loader -> Finalizer

   *
   * This means that dynamically loaded web applications and OSGi bundles can't be unloaded.
   *
   * If the library is loaded in an application class loader, we try to break the cycle by loading
   * Finalizer in its own independent class loader:
   *
   * System class loader -> Application class loader -> ReferenceMap -> FinalizableReferenceQueue ->
   * etc. -> Decoupled class loader -> Finalizer

          }

          @Override
          public void remove() {
            listIter.remove();
          }
        };
      }
    };
  }

  static <T extends @Nullable Object> Iterator<T> cycle(Iterable<T> iterable) {
    return new Iterator<T>() {
      Iterator<T> iterator = Collections.<T>emptySet().iterator();

      @Override
      public boolean hasNext() {
        return true;
      }

      assertTrue(cycle.hasNext());
      assertEquals("b", cycle.next());
    }
  }

  public void testCycleOfTwoWithRemove() {
    Iterable<String> iterable = Lists.newArrayList("a", "b");
    Iterator<String> cycle = Iterators.cycle(iterable);
    assertTrue(cycle.hasNext());
    assertEquals("a", cycle.next());
    assertTrue(cycle.hasNext());
    assertEquals("b", cycle.next());
    assertTrue(cycle.hasNext());