}

  // Intentionally using IdentityHashMap to test creation.
  @SuppressWarnings("IdentityHashMapBoxing")
  public void testIdentityHashMap() {
    IdentityHashMap<Integer, Integer> map = Maps.newIdentityHashMap();
    assertEquals(emptyMap(), map);
  }

  public void testConcurrentMap() {
    ConcurrentMap<Integer, Integer> map = Maps.newConcurrentMap();
    assertEquals(emptyMap(), map);
  }

  }

  // Intentionally using IdentityHashMap to test creation.
  @SuppressWarnings("IdentityHashMapBoxing")
  public void testIdentityHashMap() {
    IdentityHashMap<Integer, Integer> map = Maps.newIdentityHashMap();
    assertEquals(emptyMap(), map);
  }

  public void testConcurrentMap() {
    ConcurrentMap<Integer, Integer> map = Maps.newConcurrentMap();
    assertEquals(emptyMap(), map);
  }

   * syntax</a>.
   *
   * @return a new, empty {@code IdentityHashMap}
   */
  public static <K extends @Nullable Object, V extends @Nullable Object>
      IdentityHashMap<K, V> newIdentityHashMap() {
    return new IdentityHashMap<>();
  }

  /**
   * Computes the difference between two maps. This difference is an immutable snapshot of the state