/** Returns a serializable converter that always converts or reverses an object to itself. */
  @SuppressWarnings("unchecked") // implementation is "fully variant"
  public static <T> Converter<T, T> identity() {
    return (IdentityConverter<T>) IdentityConverter.INSTANCE;
  }

  /**
   * A converter that always converts or reverses an object to itself. Note that T is now a
   * "pass-through type".
   */

/**
 * Test for {@link Network} methods which have default implementations. Currently those
 * implementations are in {@link AbstractNetwork}; in future they might be in {@link Network}
 * itself, once we are willing to use Java 8 default methods.
 */
@AndroidIncompatible
// TODO(cpovirk): Figure out Android JUnit 4 support. Does it work with Gingerbread? @RunWith?
@RunWith(Parameterized.class)

      description: Please describe the issue you encountered.
    validations:
      required: true

  - type: textarea
    attributes:
      label: Example
      description: >
        Please provide a [Short, Self Contained, Correct (Compilable), Example](http://sscce.org/)
        demonstrating the bug.
      render: java
    validations:
      required: true

  - type: textarea
    attributes:

   *
   * <p>Note that in GWT, class names are often obfuscated.
   *
   * @param self the object to generate the string for (typically {@code this}), used only for its
   *     class name
   * @since 18.0 (since 2.0 as {@code Objects.toStringHelper()}).
   */
  public static ToStringHelper toStringHelper(Object self) {
    return new ToStringHelper(self.getClass().getSimpleName());
  }

  /**

   * reference has been cleared and one {@code finalize} method has been run before this method
   * returns. This method may be useful when testing the garbage collection mechanism itself, or
   * inhibiting a spontaneous GC initiation in subsequent code.
   *
   * <p>In contrast, a plain call to {@link java.lang.System#gc()} does not ensure finalization

    final CountDownLatch hasConfirmedIsRunning = new CountDownLatch(1);

    /*
     * The main test thread tries to stop() the service shortly after
     * confirming that it is running. Meanwhile, the service itself is trying
     * to confirm that it is running. If the main thread's stop() call happens
     * before it has the chance, the test will fail. To avoid this, the main

    assume().that(graph.allowsSelfLoops()).isFalse();

    IllegalArgumentException e =
        assertThrows(IllegalArgumentException.class, () -> putEdge(N1, N1));
    assertThat(e).hasMessageThat().contains(ERROR_SELF_LOOP);
  }

  @Test
  public void putEdge_allowsSelfLoops() {
    assume().that(graphIsMutable()).isTrue();
    assume().that(graph.allowsSelfLoops()).isTrue();

   * default initial capacity, load factor, and concurrency settings.
   *
   * <p>This implementation is highly efficient when {@code elements} is itself a {@link Multiset}.
   *
   * @param elements the elements that the multiset should contain
   */
  public static <E> ConcurrentHashMultiset<E> create(Iterable<? extends E> elements) {

    IllegalArgumentException e =
        assertThrows(IllegalArgumentException.class, () -> graphAsMutableGraph.putEdge(N1, N1));
    assertThat(e).hasMessageThat().contains(ERROR_SELF_LOOP);
  }

  @Test
  public void putEdge_allowsSelfLoops() {
    assume().that(graphIsMutable()).isTrue();
    assume().that(graph.allowsSelfLoops()).isTrue();

// TODO(cpovirk): Annotate for nullness.
class LocalCache<K, V> extends AbstractMap<K, V> implements ConcurrentMap<K, V> {

  /*
   * The basic strategy is to subdivide the table among Segments, each of which itself is a
   * concurrently readable hash table. The map supports non-blocking reads and concurrent writes
   * across different segments.
   *