assertThat(Primitives.unwrap(String.class)).isSameInstanceAs(String.class);
  }

  public void testAllPrimitiveTypes() {
    Set<Class<?>> primitives = Primitives.allPrimitiveTypes();
    assertThat(primitives)
        .containsExactly(
            boolean.class,
            byte.class,
            char.class,
            double.class,
            float.class,
            int.class,

   * simpler way to test whether a {@code Class} instance is a member of this set is to call {@link
   * Class#isPrimitive}.
   *
   * @since 3.0
   */
  public static Set<Class<?>> allPrimitiveTypes() {
    return PRIMITIVE_TO_WRAPPER_TYPE.keySet();
  }

  /**
   * Returns an immutable set of all nine primitive-wrapper types (including {@link Void}).
   *
   * @since 3.0
   */