}

  /**
   * Creates a thread-safe set backed by a hash map. The set is backed by a {@link
   * ConcurrentHashMap} instance, and thus carries the same concurrency guarantees.
   *
   * <p>Unlike {@code HashSet}, this class does NOT allow {@code null} to be used as an element. The
   * set is serializable.
   *
   * @return a new, empty thread-safe {@code Set}
   * @since 15.0
   */

    for (Map.Entry<? extends V, ? extends K> entry : source.entries()) {
      dest.put(entry.getValue(), entry.getKey());
    }
    return dest;
  }

  /**
   * Returns a synchronized (thread-safe) multimap backed by the specified multimap. In order to
   * guarantee serial access, it is critical that <b>all</b> access to the backing multimap is
   * accomplished through the returned multimap.
   *

    // We assume that all defaults are generics-safe, even if they aren't,
    // we take the risk.
    @SuppressWarnings("unchecked")
    T defaultValue = (T) defaults.getInstance(type.getRawType());
    if (defaultValue != null) {
      return defaultValue;
    }
    @SuppressWarnings("unchecked") // All arbitrary instances are generics-safe
    T arbitrary = (T) ArbitraryInstances.get(type.getRawType());

        }
    }

    // ===================================================================================================
    /**
     * Helper class to traverse graph. Required to make the containing method thread-safe
     * and yet use class level data to lessen stack usage in recursion
     */
    private class ClasspathGraphVisitor {
        MetadataGraph graph;

        ClasspathContainer cpc;

    return emptyListIterator();
  }

  /**
   * Returns the empty iterator.
   *
   * <p>The {@link Iterable} equivalent of this method is {@link ImmutableSet#of()}.
   */
  // Casting to any type is safe since there are no actual elements.
  @SuppressWarnings("unchecked")
  static <T extends @Nullable Object> UnmodifiableListIterator<T> emptyListIterator() {
    return (UnmodifiableListIterator<T>) ArrayItr.EMPTY;
  }

 * <p>Data stores are registered by name and class name, allowing flexible lookup.
 * The factory also supports dynamic discovery of data store plugins by scanning
 * JAR files for data store configurations.</p>
 *
 * <p>Thread-safe operations are supported for registration and retrieval of data stores.
 * The factory caches data store names with a time-based refresh mechanism to improve
 * performance while ensuring up-to-date plugin discovery.</p>
 */

  @Override
  public abstract int hashCode();

  /*
   * The implementation neither produces nor consumes any non-null instance of type C, so
   * casting the type parameter is safe.
   */
  @SuppressWarnings("unchecked")
  static <C extends Comparable> Cut<C> belowAll() {
    return (Cut<C>) BelowAll.INSTANCE;
  }

 * invoke methods, they invoke methods on the {@code ForwardingMultiset}.
 *
 * <p>The {@code standard} methods and any collection views they return are not guaranteed to be
 * thread-safe, even when all of the methods that they depend on are thread-safe.
 *
 * @author Kevin Bourrillion
 * @author Louis Wasserman
 * @since 2.0
 */
@GwtCompatible

        if (!isTarget(path)) {
            return null;
        }

        return newDictionaryFile(encodePath(path), path, timestamp);
    }

    /**
     * Encodes a file path using Base64 URL-safe encoding.
     *
     * @param path the file path to encode
     * @return the Base64 encoded path
     */
    protected String encodePath(final String path) {

  }

  // Element Mutation

  @Test
  public void addEdge_existingNodes() {
    assume().that(graphIsMutable()).isTrue();

    // Adding nodes initially for safety (insulating from possible future
    // modifications to proxy methods)
    addNode(N1);
    addNode(N2);
    assertThat(networkAsMutableNetwork.addEdge(N1, N2, E12)).isTrue();